Its a mater of what other parts you have to compliment the part your adding.



I've loked at many an article where diff cams, headers or exhaust has made cars lose horsepower.


So basicly the 10-15 hp for a header..........5-10 hp for exhaust is a general statement made by manufacturers.


It all depends what combination you got going. and some good dyno time to really find out what different parts are doing as far as horespower.