Oh yes...know exactly where your coming from.
I used to think something was wrong with my GT, because coming home from Tims tune (468/479) the car just felt INSANE. Felt like a line backer was just driving you into the seat! Just crazy. But by the time I got home...most of that feeling was gone
Then I did a few little things and it was just starting to feel slower and slower...I thought it was loosing power. Put it on the dyno and it threw down 479/512 LOL.
BUT I must say...at the end with 12PSI and T-61s (550RWHP!) it didnt feel slow when the power came on! I didnt get used to that, and I think mainly because the car just got faster with RPM and really let me feel the power better...along with the fact that i didnt get to play with it much at that power level
Cobra felt slow as heck in 3rd and 4th gear though when I switched LOL....now its starting to feel faster because im slowly forgetting how much power my GT had.