BMyers

Mine is a 2021 2500HD, SLT 4WD

I notice the same issue, highway driving, smooth road, no pull right or left just seems like any corrective action has more of an affect than I want, seems like i'm gently swerving side to side in a lane. I'm a tech so to me it feels like the caster is on the low side and the toe is not correct. I don't notice any unusual tire wear. I intend on complaining on my last free oil change at the dealer to see if they will check the alignment. My last truck was off from the factory, they reset it and it was noticable but it was a 1500, this 2500 has different components but it still has the variable assist steering technology which may be part of the problem.

Yeah I did think about anything getting inside the engine compartment, anything corrosive would be met with totally blocking it off but so far the snow removal chemicals are not making it in. If I did interstate travel in bad weather I think it would be possible. As far the fuel mileage, its still bad lol. I'm a 35 year tech so to me heat is a killer so I'm hoping it keep things cooler. I may need the next 10 - 15 years to prove it though.

I installed the Duramax chrome hood with the open vent. I opened up a slot in the insulation pad and installed a deflector to direct the air flow into the engine compartment. Some of the fresh air will find itself to the cold air intake area but most airflow will land right on the top of the intake. Mostly the chrome hood vent looks cool, but I'd like to think that cool air on a gas motor is a good thing.

I agree, that is my experience too. My mileage is better and runs great.

No I get what your saying and grumpy is probably correct that in gm language dod and afm are the same but in the Diablo tuner it is 2 separate functions to choose. I turned both of them off. Vvt is probably part of the programming in the tune for performance though. Diablo tuners have options for many settings including timing and fuel mixture and shift pressures but nothing for vvt. That would be interesting though.

So grumpy I get that point so get mine. It works and your dick way of discussing this isn’t cool. I’m just offering real life experience and results that I’ve been pleased with. Acknowledge that with your stinging criticism. Btw your internet attack sidelines a real guy just looking for info while dicks like you lurk around to pounce with your digital knowledge. Bye. Your type ruins these forums.

So that's pretty interesting, I'm a 30 year tech, run a shop so it's my own experience. Diablo has a way to disable DOD and AFM seperately, my fuel mileage is real, what difference is the first post are you wanting me to stay out? Anyway my truck runs great, bought it new, 2018 Sierra SLT 5.3, also run a catch can to remove oil vapors. The mods I did was mostly for preserving the engine and my investment, the improved performance is fun and great, and the mileage was unexpected. I don't have any pinging btw so maybe up the tune to the Diablo and see how it goes.

I bought the Diablo tuner, ran the diablo tune, turned off AFM, turned off DOD, added 20% throttle response. Runs great, better mileage by 2-3 mpg, sometimes more and it runs great all the time without the cylinder deactivation sounding bad and herky jerky stuff. Shifts better too btw and left torque management on, tried it off but its better on.