hey guys, I'm in the market to replace my stock catalitic converter. I have 2 choices, either a staight pipe or an aftermarket cat. First of all, who will give me the best HP? I know with a straight pipe I might not pass emmissions but that's OK, I get it done by a local mechanic anyway. I'm looking for something that will be better for the car as far as mileage and will ad power to it. Any suggestions?