just to point out right there, that if every after makert product gave u ever hp they say they do, then everbodies car would fall, i remember reading about stuff like, they say an exhaust will give UPTOO, 12hp (yeah right), i guess if u have like a turbo or supercharger, or some other mods that WORK WELL, with the exhaust, just depends on the condition of the engine u have and how well everything works to gether, but just take it to dyno, they can tell u for sure, good luck man