I have an 03 coupe and the acceleration is very weak, when i give it WOT sometimes the car just slowly accelerates as if i am barely on the pedal, sometimes it will just stutter and start to accelerate normally but only for a few seconds before it just goes back to slowly accelerating, and other times(very rarely) it will accelerate as it should but soon after goes back to slowly accelerating. Ive noticed the exhaust note changes during each scenario. Any ideas would be great as ive exhausted pretty much everything i could think of. I can name everything ive tried if needed. Thanks a lot!!

 

Plug in an OBD2 scanner and start reading data, pay particular attention to what APP % and TP% it's reading, you might have a failing APP that's sending the wrong signal.

EDIT: Since you have an '03 you can take off the intake pipe turn the key to on, have someone else press on the accelerator pedal to make sure it's opening the throttle body all the way.

 

I already replaced the accelerator pedal position sensor but i could try and live read to see what its showing, thanks!