Finding the best upgrades for 6.7 Cummins engines is usually a top priority the moment someone drives one off the lot, mostly because these trucks have so much untapped potential hiding under the hood. While the 6.7-liter platform is arguably one of the best diesel engines ever put into a heavy-duty pickup, it's no secret that they're a bit choked up from the factory. Between strict emissions standards and the manufacturer's need to play it safe, you're often left with a truck that feels a little more sluggish than it should.
Whether you're looking to tow a 15,000-pound fifth wheel through the mountains or you just want a more responsive daily driver, there are a few specific modifications that stand out from the rest. Let's dive into what actually works and what's just hype.
Getting More Air into the System
If you want your engine to perform better, you have to let it breathe. It's that simple. The stock airbox on a 6.7 Cummins isn't terrible, but it's definitely not optimized for high performance. Switching to a Cold Air Intake from a brand like S&B or Banks Power is often the first thing people do, and for good reason. It's a relatively cheap, easy install that you can do in your driveway with basic tools.
A good intake does more than just add a couple of horsepower. It improves throttle response and helps lower your Exhaust Gas Temperatures (EGTs). When you're pulling a heavy load up a steep grade, keeping those EGTs in check is the difference between a long-lasting engine and a very expensive repair bill. Plus, let's be honest—hearing that turbo whistle a little more clearly is a nice bonus.
The Grid Heater Delete
While we're talking about airflow, we have to mention the grid heater. If you've spent any time on the diesel forums, you've probably heard about the "jiggle pin" or the grid heater bolt issue. On many 6.7 Cummins engines, the bolt that holds the heater element can vibrate loose over time, fall into the intake, and essentially destroy the engine.
Many owners opt for a grid heater delete or a specialized plate that moves the heater. It's one of the best upgrades for 6.7 Cummins reliability because it eliminates a potential catastrophic failure point while also opening up a significant bottleneck in the intake plenum. If you live in a place where it gets below zero, you'll need a plan for cold starts, but for everyone else, it's a solid move.
Fueling the Beast
The fuel system is the heart of any diesel, and the 6.7 Cummins is no exception. Depending on the year of your truck, you might have the Bosch CP3 or the more controversial CP4 high-pressure pump. If you have a 2019 or 2020 model with the CP4, your first "upgrade" should honestly be a CP3 conversion kit to avoid a total fuel system failure.
Lift Pumps are Essential
Aside from the high-pressure pump, the factory lift pump (which pushes fuel from the tank to the engine) is often the weak link. Installing an aftermarket Lift Pump like a FASS or AirDog system is a game-changer. These systems do a few things: they provide a much higher volume of fuel, they filter out more contaminants than the stock filter, and most importantly, they remove air and vapor from the fuel.
Diesel engines hate air in the lines. By sending "pure" fuel to your injectors, you'll notice a smoother idle and potentially better fuel economy. It also acts as a safeguard for your expensive injectors by ensuring they never run dry or get clogged with debris.
Tuning and Electronics
You can't talk about the best upgrades for 6.7 Cummins trucks without mentioning tuning. The factory computer is programmed to be conservative to meet a wide range of climates, fuel qualities, and driver habits. A custom tune can wake the truck up in ways a bolt-on part never could.
Choosing the Right Programmer
Most guys go with something like an EZ LYNK or an EFI Live setup. These allow you to load custom tunes that optimize the engine's timing, fuel delivery, and turbo boost. It's not just about "rolling coal"—in fact, a good tune should be clean. It's about making the power delivery smoother and getting the transmission to shift better.
One thing people often overlook is Transmission Tuning. The 68RFE transmission found in many of these trucks is notorious for being a bit "soft." Transmission tuning increases line pressure, which helps the clutches hold better and prevents slipping. If you're going to add power to the engine, you must address the transmission, or you'll be looking at a rebuild sooner than you'd like.
Strengthening the Drivetrain
Speaking of the transmission, let's get real for a second. The 6.7 Cummins makes an insane amount of torque, and that torque is the enemy of a stock 68RFE. If you've upgraded your tuning and fueling, your transmission is on borrowed time if you have a heavy right foot.
Beyond the Software
If you aren't ready to drop $10k on a fully built transmission, a deep transmission pan and a valve body upgrade are great middle-ground options. A larger pan holds more fluid, which keeps temperatures down during towing. An upgraded valve body improves the physical shifting mechanics, providing firmer engagement and less heat-generating friction. It's a proactive way to make sure your truck can actually handle the "best upgrades" you've put under the hood.
The Importance of Monitoring
With all these changes, you can't just rely on the factory dashboard to tell you what's going on. The stock gauges are more like "estimate" lights than actual precision instruments.
Installing a digital monitor, like the Edge Insight CTS3, is one of the smartest moves you can make. It plugs into your OBDII port and lets you see exactly what your EGTs, boost pressure, transmission temp, and fuel rail pressure are in real-time. It's much cheaper to back off the throttle because you see your temps climbing than it is to replace a melted piston because you didn't know you were running hot.
Breathing Out: Exhaust Upgrades
Finally, we have to talk about getting the exhaust gases out. On a 6.7 Cummins, the factory exhaust system is packed with filters and sensors. For those keeping their trucks street-legal and emissions-compliant, a filter-back exhaust or a high-flow downpipe can help a bit with sound and flow without triggering any check engine lights.
The goal here is to reduce backpressure. The less the turbo has to fight to push exhaust out, the more efficiently it can spin. This leads to better fuel economy and a more responsive turbocharger. Plus, replacing that massive factory resonator with a high-flow pipe just makes the truck look and sound a lot more like a real diesel.
Final Thoughts
At the end of the day, the best upgrades for 6.7 Cummins trucks are the ones that balance performance with longevity. It's easy to throw a massive tune on a stock truck and go fast for a week, but the real goal is to make a truck that's more capable and more reliable than it was when it left the factory.
Start with the basics: let it breathe with an intake, protect the fuel system with a lift pump, and keep an eye on everything with a good monitor. Once you've built that foundation, you can start chasing the higher horsepower numbers. These engines are built to work, and with a few the right tweaks, they'll do it better than almost anything else on the road.