I have a 2002 GT Convertible with what appears to be a catback system. I can't tell who the manufacturer is as the mufflers are getting a rusty palor to them. There are no leaks. It has 2 1/2" pipes and the tail pipes go from 2 1/2 to a 4" outlet. I have to blare the radio to hear anything. I have an H pipe that much I can see. Any suggestions on what I can use that will suppress noise a little more but not compromise performance?