.......... u know what sonictheory, there's too many theories in here hahaha... so juz follow ur instinct, imagine u're the car. n the air flowing thru the car... of course most importantly is the air filter / intake system must be good , before u can feel more from the exhaust setup right? changing the whole exhaust system WITHOUT changing to a better air filter .... well, u read all the suggestions already n think urself la ok sonictheory. n like wat fred said, if auto no need to mod to get more power, then all exhaust shops pokai ady.. im outta here....