Far from an expert, but decided to give AI a shot at it. Check out the following info, which gives a pretty good opinion of possible causes, but I really doubt the extra speed it turns, really would have a direct effect on what you are experiencing.
Because the transmission and the rear...
Thank you. The C7 does not have a Z-mode. I can say without a doubt 4-cylinder mode is not kicking in when it is in Sport mode with manual shifting. This is through watching the DIC with Cylinder activation selected and just listening carefully with the window open and not much ambient noise...
I had read about when the AFM is active when we first bought our 2014 in May of 2017. From my recollection it was always active in the automatics. What I recently discovered is the AFM does not seem to kick in when I have it in Sport mode with Manual shifting. I am not trying to refute any...