I am getting a 99 Z28 M6 soon and I want to put a loud exhaust on it. I used to have an Lt1(check sig) and it had loudmouth exhaust. I have decided to go with loudmouth with no questions asked. What is the deal with y-pipes and high flow cats???? If I buy a y-pipe and high flow cats, how will my car sound? Also, what does that do for performance? How well do the stock y-pipe and cats flow stock? I want my car to sound as loud as my old lt1. THanks guys!