After much searching and not finding anything exactly like what I'm experiencing, I decided to reach out here. I have a unique 1999 Carrera 2, that has a 2007 Carrera S engine swap, 6sp manual. The car starts and idles fine, and if you were taking it out for a VERY leisurely drive, you might not even notice anything is wrong. It's driveable, and has no CEL or codes showing up on OBD or Durametric, but it has a very obvious lack of power/acceleration wit any type of spirited driving. The pedal is responsive for about the first 1/8th of the way down, but once you get above 2000 or so RPM there is a very slow, gradual acceleration even under wide open throttle (especially in 3rd through 6th). I started with some basic maintenance and cleaned the K&N air filter, cleaned the MAF, cleaned the throttle body, fresh oil change, and put techron in a tank of gas. I also put the pedal to the floor with the key turned on and the engine off, and the throttle opens completely, so the wire seems to be fine.
Reading through the forums, the most similar issues I could find suggested possible :
Throttle Position Sensor
Camshaft Position Sensor
Fuel Pressure Regulator
Plugs & Coils
Most of those all came with a rough idle, hesitation or CEL, and I don't have any of those issues...So for now, I'm driving a cool looking car that would lose a 1/4 mile race to a ford fiesta. If anyone has experienced anything similar, or has a good suggestion on where to start, and how to check the sensors or fuel pump to try to narrow down the problem, I would greatly appreciate your input.