A friend had 2 chamber Flows and Mac offroad-H on his 87 5.0 and it was LOUD LOUD. My catted X-pipe and Magnaflow cat-back are about 50-75% as loud as his old setup, so it's just loud. I have had excellent performance realization with my setup. If you go with the offroad X, it will be louder. I'm not sure of the performance difference between the catted X and offroad X, although I've heard some people say the sound of the offroad X is somewhat tinny.