im not sure yet...ive got a 2 1/2 y pipe i built with a 3in highflow cat and enough pipe to turndown at axle that was on it before but had turbo mufflers on it too but i may do something diff. i want to be heard with the lumpy cam at idle but not too obnoxious since i dont get off work till midnight. debating on a 3in y pipe merged into a single 3.5in with a bullet muffler and a turndown or 2 1/2-3in true duals with xorh pipe and bullets with turndowns.