Airraid and flowmaster original 40 w/2.5 from Y pipe back. I chose the airraid because it uses a lot of the stock parts. Either way these mods are mostly for sound may help HP a tad, but not that much. I noticed a bit more mid range pull, but nothign significant. I have yet to check MPG b4 and after as i'm a bit heavy on the throttle now, it sounds great.