besides the mods mentioned above i also have a header and cam gears. The car is a 2000 SI.. I've been given theories on the cause:
1) it could be a build up of back pressure due to the stock exhaust (?)
2) ecu error... (but i doubt it because it worked fine before the installation)
3) its normal to run poorly before its tuned after installing big cams.. (?)

Why is the vafc junk?