i just bought a Mac Prochamber, an Xcalibrator 2, and a Magnaflow catback system, as well as a K&N Air Filter, and i removed the intake silencer. About how much of a HP gain should i expect from those mods on my 01 Bullitt?

 

15 to 20 id say. But overall, you picked an AWESOME sounding exhaust set up. Congrats.

 

Should sound awesome for sure.