Like I said before, don't take out your damn cat! THEY DON'T RESTRICT HORSEPOWER ANYMORE. That was back in the '70's that they robbed power. If you go for a whole new exhaust and have a built motor, yeah, you'll want a high flow cat. If not, the stock one flows really good - as long as it isn't clogged. Hell, I'd be willing to bet that a flowmaster is more restrictive with all those retarded chambers. They only flow a little better than a stock style muffler - they're designed for a tinny sound, not maximum horsepower. You want more power, look at your engine, not the exhaust. Damn kids.