another thing, why is a cat back better than just replacing the muffler on the stock piping? What so different about pipes? Also on a catback are there any resonators and any other things that maybe on the stock exhaust system? If there are no resonators then would it not be louder than just putting a muffler on the stock pipes which has the resonators on it? Sorry I know its again a newbie question.

What is Mandrel tubing and straight through flow design?