I have flows on my mustang, and it really sounds good around 2000 rpm's. I can also feel a smoother throttle response and a slight more grab at high rpm's. However, I would like my muffler's louder. I read an article at
www.mustangworld.com where a guy did some slight modifications to make his louder. As for the warranty, i dunno...i've far surpassed mine. I also don't know much about mac exhaust systems.