[luti]

Backpressure is both good and bad. I know thats confusing, but bear with me. Backpressure helps at low RPM's to get the exhaust gasses out of the cylnders, but hinders performance at high RPM's. That is why headers and exhausts and catalytics have to be purchased and tuned to your specific needs. If you want a street car you want larger than stock diamaters, and a more free flowing system, but not a completly empty system. You won't be able to make it off the line, your car will feel week at the low end. If you are building a race car cut out the cat, if your racing your always using high RPM's and have nothing to worry about. Also, the lack of a cat will make your car significantly louder and make your car that much worse for the planet (ecologically). Please keep your cat in unless your off to the track.