Hi
@nick14226, can you elaborate on what ruins your drive on a daily basis. I guess each one these vehicles are different, but in my Denali (which is so whisper quiet in the cabin I cannot even hear the stock exhaust, and really cannot even hear the engine unless its above about 3500 RPM) the ins/outs of DFM are completely unnoticeable. Even with the windows down, the wind noise easily drowns out any drivetrain sounds. (I Must be one of the lucky ones, or maybe on this trim level, it is less perceptible). Also, after disabling, do you notice any fuel economy differences? I routinely get 21+ MPG on flat highways if I keep her under about 73MPH, did 400 Mile round trip last weekend and got 22.1 on the way there, and 21.4 on the way home.
Anyway, I am not saying you are wrong, just more curious on what characteristics of the DFM in your vehicle make your driving experience poor. In my rig, I set the cruise and life is grand, if I need power, I hit the gas, and there is immediate downshift and the 6.2 comes to life and I am off to the races. In town, I never notice it engaging or disengaging...I'm at 30.5k on the odometer, and things are still smooth as silk. That said, my rig is 100% stock on everything engine/exhaust related.
EDIT: I just re-read the whole thread, see your complaint is primarily shudder/vibration at cruise or gentle throttle application (presumably not enough power demand to reactivate all cylinders?)
Is it possible you actually have the transmission shudder issue, and it is just more noticable when DFM is enabled, vs DFM? Do you have the 5.3 or 6.2? That coule be another factor, as could be your performance exhaust?
All good, seems disabling it helped your application...glad there is a solution that works for you.