Which y-pipe is better as far as 1/4 mile performance and horsepower gains. The Stillen one costs more but has slightly larger piping 60mm or 2.3 inches. The Custom Enterprise one has 2.25 inch piping. Also, I know people are going to tell me to just get the SS Autochrome Headers, but I live in SoCal, and there is no way in hell i could pass a smog test with those or ne other headers for that matter. Plus installation on headers is a lot more time consuming and more expensive than the y-pipe installation (y-pipe can also be taken on and off for smog test purposes at a lot lower cost than headers). Please give me some input on which y-pipe is a better performer and which one sounds better. By the way I have a Greddy Evo exhaust system with 60-70mm piping would I need a resonator with the y pipe?