Best Upgrades For LLY Duramax – 2021 Ultimate Buyer’s Guide

| Last Updated: December 25, 2021

Best of Diesel is reader-supported. When you buy through links on our site, we may earn an affiliate commission.

Duramax may have several bolt-ons and gives the smoothest and quietest operation in your vehicle. However, have you tried to tackle the weaknesses that come with it? Upgrading your Duramax will change the game for you for a lifetime, and in this guide, we’ll let you know exactly how.

Comparison Chart of the Best Upgrades For LLY Duramax

  • Best LLY Duramax Tuners
  • Diagnose trouble codes to ensure proper operation
  • Increase in horsepower and torque
View Latest Price →
  • Best for the Money
  • 78.6% increase in air flow
  • Compatible with any intake system
View Latest Price →
  • Best LLY Duramax Turbo
  • Promises top quality and efficiency
  • Comes with vane sensor
View Latest Price →
  • Up to 5 power levels of additional horsepower and torque
  • Adjustable speed limiter
  • Will optimize a stock engine’s performance
View Latest Price →

Types of LLY Duramax Upgrades

Before we jump on to the reviews of the models that stand out in the market, let’s take a look at the types of LLY Duramax upgrades. This will help you determine which one speaks out more to you. Let’s take a look at these types:

Bosch Injectors

If you are facing several injector-related issues such as piston damaging or excessive balance rates, you need to upgrade the injectors. Bosch’s updated and new injectors come with stronger and more durable bodies that have chrome-plated ball seats to eliminate all these issues.


If you have temperature issues in your current Duramax turbo mouthpiece and have an overheated engine, it’s time for you to upgrade your turbocharger. Getting a free-flowing turbo piece gets rid of the overheating issues and provides the accurate boost pressure to your engine.

Cooler Lines

Most Duramax owners face a leaking issue in their cooler lines even after using the warranty to replace it. You need to get rid of these factory hoses and purchase high-quality stainless-steel lines that hold up to the immense pressure or harsh weather conditions. 

Why Did These Upgrades Make Our List?

There are a few reasons why we picked out these upgrades for you. Let’s take a look at the difference that these upgrades make in your vehicle, and how they change the game for you:


These upgrades are more durable and last for a longer period of time. Even if you do end up paying a couple more bucks than you intended to, they would be worth it. This is because they give your vehicle a new lease of life and can operate under immense pressures as well as bad weather conditions.


These parts make all the difference when it comes to peak performance. They are very powerful and made with the highest quality materials. This provides the optimal functionality of the parts that merge together to make the vehicle work super efficiently.


Another reason why these products were chosen is that they have gone through vigorous testing and high-quality standards to provide you with the best possible upgrades for your vehicle. These parts will not disappoint you or let you down.

Review of the Best Upgrades For LLY Duramax

Let’s take a look at the reviews of the best upgrades that you can find for LLY Duramax. Our chosen models have been reviewed in detail so that you can find the perfect pick for yourself.

Best Overall:
Bully Dog - 40420 - GT Platinum Tuner

Bully Dog GT Platinum Diesel Tuner


  • Trouble codes can be diagnosed and cleared
  • You can enjoy fuel saving for long haul driving
  • LCD display allows you to monitor 15 different performance parameters
  • Four products in one: monitor, gauge, diagnostic device and engine tuner
  • Able to utilize many preloads and 10 customized tune files for your vehicle


  • Installation is very slow and difficult
  • Fuel mileage increase is not that drastic
  • Does not provide as much horsepower as it claims

What Recent Buyers Report

Most of the users who reviewed this product seemed to be pretty impressed and highly satisfied with it. It does add on a ton of power and torque, and it doesn’t bug you while you are driving. It also provides you with a lot of options for customization according to your vehicle.

Why it Stands Out to Us

Bully Dog is a very famous and popular brand for car parts, and they always ensure the highest quality materials in their products. This engine tuner is nothing short of that and is packed with so many features that you will not need any other upgrade for your engine.

Who Will Use This Most

This is a very versatile device and can be used on cars, trucks, and any other type of vehicle. It is also very simple and easy to use and comes with a diagnostic reader to scan the trouble codes and clear them out as well. It is also a great upgrade for your Duramax LLY.

Bottom Line

For those looking for a reliable, high-quality engine tuner, this is the right upgrade. It also provides a big change in the horsepower and torque and increases the fuel mileage as well. It is also customized, and it is also very easy to read the codes.

S&B Filters 76-1006B Engine Turbo Mouthpiece


  • Installation is super easy and efficient
  • Helps the turbo breathe a little better
  • Compatible with most of the intake systems
  • Provides a whopping 78.6% increase in the airflow
  • Sleek powder-coated design that gives a sophisticated look


  • Not recommended unless you’re upgrading something else too
  • Installation requires more disassembly than is mentioned in the instructions

What Recent Buyers Report

As per reports, this popular turbo mouthpiece is an essential upgrade for all Duramax users as it can totally change the way that your engine performs. It provides better airflow, and you will notice an increase in the fuel mileage as well. It is also super easy to install, as it doesn’t take up a lot of time.

Why it Stands Out to Us

This product stands out because it is designed with a black powder coating to give the piece a more elegant and high-quality look. It is also durable and is compatible with a lot of different intake systems. The turbo can breathe better and does not overheat, and the installation is a breeze.

Who Will Use This Most

If you are a Duramax user, then this is a must upgrade for you. It works excellent on LLY Duramax and provides better throttle response and increased file mileage. It is also very useful for those who want to get the best value for their money and at the same time, want something of high quality.

Bottom Line

The thousands of excellent reviews on this turbo piece, the high-quality design, and the attractive pricing make this product a killer deal for a Duramax upgrade. If you are looking for the turbo piece that helps overcome your overheated system, then this is the perfect option for you.

Best LLY Duramax Turbo:
Garrett 848212-5001S Turbocharger


  • Works very well and is quite effective
  • Made with high-quality steel that is durable
  • Top-quality construction with high efficiency
  • Changes how your engine performs completely
  • Comes with 3 banjo bolts that do the job accurately


  • Installation is a pain
  • Banjo bolts broke for some users
  • Packaging was too flimsy for a heavy item

What Recent Buyers Report

For Garrett, the quality and design of this turbo are amazing. It is well constructed with high-quality steel and is very durable and sturdy. It also performs efficiently and adds power to the engine. It works great and spools right up when you crank it for the first time.

Why it Stands Out to Us

The reviews of the turbo are great and state that it is quite heavy-duty. It comes with all the latest upgrades needed for your vehicle, and the pins are used to minimize distortion and enhance the vane activation. It features three cobalt pins as well, which makes it quite useful.

Who Will Use This Most

This turbo is excellent for use for owners of Chevrolet and GMC 6.6L and is the perfect upgrade for Duramax LLY, LBZ, and LMM. If you’re looking for a high-quality, high-powered turbo that works like a beast, then you will definitely enjoy this one.

Bottom Line

To sum up, if you’re looking for the best turbo upgrade for your Duramax LLY, it doesn’t get better than this. The quality, construction, performance, and durability of this turbo are everything that you need in your vehicle. It is also very efficient and does not wear out easily.

4. PPE Xcelerator GM 2001-2010 Standard


  • Provides better throttle response
  • Optimizes the engine’s performance
  • You can easily just upgrade the software
  • The speed limited on this part is adjustable
  • Comes with up to five different power levels of added horsepower


  • Some users didn’t get the MPG gain
  • A few people preferred the Bully Dog
  • The extra power only comes at the wide-open throttle

What Recent Buyers Report

There is a lot of potential and peak performance capability with this product, and it works flawlessly with the LB7 Duramax. It also increases the fuel mileage, and you can adjust the tire size so that it calibrates with your speedometer. Overall, this is an impressive Duramax upgrade.

Why it Stands Out to Us

This powerful beast comes with five different power levels of horsepower and torque, making this upgrade a super fiery and high-quality one. The best feature of this upgrade is that it automatically optimizes according to your stock engine’s performance, and you can easily upgrade the software.

Who Will Use This Most

This is very useful for users who have the PPE Manifolds as well as the Up-Pipes. It also is the perfect upgrade for the LB7 Duramax and can be used with a camper truck as well. It is an amazing product to use for heavy-duty trucks as it provides better throttle response and excellent tuning.

Bottom Line

If you are looking for an accelerator that provides more power, high-quality throttle response, user-friendly interface, and smooth operation without any hiccups, then this PPE Xccelerator is the best item for you. You will be more than satisfied when you tune this into your truck.

Best LLY Duramax Injectors:
2004-2005 Chevy/GMC Duramax by Dieselin Parts


  • Rebuilt with the use of OEM by qualified engineers
  • High-pressure sealing surfaces redesigned to original specifications
  • Constructed with high-quality materials that are tested for reliability
  • Consistent and smooth operation no matter how many miles you travel
  • Performance is stellar due to high tolerance and extreme pressure handling


  • Repair costs are high
  • If not installed correctly, it could be really dangerous

What Recent Buyers Report

Customers found this product to be quite useful as it provides excellent value for the money. The gas mileage improved, and the power and performance of the vehicle also increased. Overall, the product performs well, but it could be refurbished for better quality. Despite that, users love their investment.  

Why it Stands Out to Us 

The reason why this set is mentioned in this list is because of the high-quality features that it provides. It is also made up of good quality internal parts which are tested by strict OES standards to ensure unparalleled functionality and operation. It also promises 100% satisfaction to its customers.

Who Will Use This Most

This is an excellent injector for the 2004.5-2005 vintage 2 Chevy and GMC 2500 and works as a phenomenal upgrade for the Duramax LLY Express. If you need a new injector that guarantees the highest quality with a good warranty, then this is perfect for you.

Bottom Line

Looking for an injector for your vehicle? This is the best one you will find in the market today and is guaranteed to provide you with excellent performance and high-quality operation. It is tested for durability and pressures and has great tolerance as well as superior components. It also comes backed up by an impressive warranty.

6. MBRP 5" DP-Back AL Series, Single Side Exit


  • Comes with tubing which is mandrel-bent
  • Can be easily installed with common tools
  • Instantly boosts the horsepower as well as torque
  • Does not come with a muffler for peak performance
  • Improves the fuel economy of the engine by 1-2 mpg


  • Aluminized Steel will rust eventually, not recommended for areas that experience winter/salt

What Recent Buyers Report

This impressive exhaust system has the most outstanding features and high-quality performance. Not one of the users faced any issues with this product. The installation is a breeze, and the roaring sound it provides to the engine makes everything even better. It also increases fuel mileage.

Why it Stands Out to Us

We find this to be an excellent upgrade for many reasons. The exhaust mates up to the DPF with ease and gives you the maximum diameter as well as the mandrel bent pipe. It provides the lowest temperatures of gas and ensures the highest possible torque and horsepower.

Who Will Use This Most

This is an excellent part for those who are looking to upgrade their Duramax exhaust system and get better horsepower and torque. It is easy to put on, which makes it super convenient for novices or beginners and is great for users who want the engine sound to be really loud.

Bottom Line

Overall, this high-quality piece is power-packed with high-quality performance and endurance. It is designed to give you the optimum functionality in your engine and is equipped with many features to guarantee customer satisfaction always.

Aspects to Consider Before Buying

Before you purchase your parts for an upgrade, go over these main considerations that you should make, so that you do not end up buying the wrong part and regret your decision:


If you own an LLY engine by Duramax, you should know that they are warmer than the rest of the engines in the market and are more prone to overheating. You need to add a few preventions or get an upgrade that allows you to combat overheating in the engine. Otherwise, it could get dangerous for you as well as your vehicle.


Before purchasing either of these parts, make sure that you have enough wiggle room or coin to pay for the installation costs. While most of the upgrades here come with easy installation if you still want to consult a mechanic, know that those costs may be super high as well.


With all the Duramax powered GMs, the automatic transmission versions of the engine have to be upgraded earlier in the whole modification process, especially if you have to go more than 400 rwp. You should also know that at any power level above 600 rwp, your LLY’s connecting rods will be risky to use as they will be prone to bending.


Now that you’ve read the entire article and the reviews of the best Duramax LLY upgrades, don’t forget to take all the considerations in mind before you buy one. Hopefully, this article provided you some information and insight on which one is more suitable for your kind of vehicle. Good luck!

People Also Ask

If you’ve still got some ambiguities or doubts haunting your mind, then look at these frequently asked questions to clarify some of your queries. This will further help you in understanding the operation of the Duramax upgrades and aid you in making a better purchasing decision.

How Much Horsepower Does an LLY Duramax Have?

The earlier models of the engines have a horsepower of about 2700 rpm, and the 2004 model of the LLY engine comes with a 310 hp at the rate of 3000 rpm. This is an increase of 300 rpm as compared to the 2002 and the 2003 models of the Duramax LLY engine.

How Many Miles Will a Duramax Last?

Upon extensive analysis by the Association of Diesel Specialists, they have found that the 6.6l Duramax is a very powerful engine motor that is available today. If it is maintained properly, it can easily reach the 350,000-mile mark, with some users even claiming that they hit 400-500,000 miles.

Are Duramax Engines Reliable?

Duramax engines have been in the market since 2001, and needless to say, they have become a huge success in the market for engines. They are known to be reliable and consistent in their production; however, the engine and the Allison 1000 transmission have some design issues.

Sean comes from the forums actually and drives an OBS Ford. He writes fantastic DIYs and knows his way around a camera, too. We keep him caffeinated and away from DPF filters to avoid another rant about recent emissions restrictions.