2021 Tahoe - Vibration/Shuttering at 40 MPH & Light Acceleration

[acesttz]

My 2024 6.2 started doing this around 30,000 miles. The vibration would stop as soon as I gave it enough throttle to run on all 8 cylinders. Ironically, I felt the vibration from the passenger floorboard, not from the driver's side. I had a GM engineer ride with me to confirm it. GM knows that the vehicles start vibrating when the DFM is active after they get some miles on them. After bypassing the DFM system - meaning I run on 8 cylinders all the time - the vibration stopped. I told the GM engineer that I was going to bypass the DFM and he suspected it would most likely fix the issue.

Also, the exhaust flapper valve when completely open creates about a 25% restriction in the exhaust pipe. I removed it and have never looked back.

 

[jfoj]

Here is a short shot of how the ignition timing is HIGHLY Retarded under load, even 3 degree loss of ignition timing can be felts as a loss of power.