Have you looked at the Magnaflow brand yet? I used there three inch in and out 14x7 ovals and they work great I saw a .04 ET gain in the 1/8 mile by removing them at the track, 6.98 to 7.02 in the summer at 2500 FT elevation track. My muffs are mounted behind the rear axle for noise control and that helps keep them quiet, until I go to WOT