@Yohan
I struggled with the moderate performance your speaking of... in the rare occasions I'm "conservatively" driving the car.
You should have noticed a pretty good difference when in "sport mode" rather than regular old drive. The MPG's don't fall off by any huge amount either (unless WOL'ing it for fun
but thats the case in D as well - shifts are just sooner).
The way this car gets it's higher mpg is thru AFM "active fuel management". It's genious & crap at the same time IMO. The car drops from 6 active firing cylinders to 4. So at low torque & heavy curb weight... your now trying to move this car on a 4 banger rather than a 6. That causes the lug & when radio off the chatter/vibration noise from below (2nd thru 3rd gear). WRONG, TRY AGAIN - Thanks AngryBird!
As I stated before I have had this issue in many GM cars. You can complain till blue in the face, nothing they are going to change or "fix" from factory standpoint.
I personally do not have the trifecta tune, but have driven others with it & the TCM modification they provide corrects this immensely. I have had other tunes on my prior pontiac g6 & g8... as well as my Cadillac CTS. They all experianced issues in different shift points as well & were corrected/improved by aftermarket solutions.
Good luck!
