Hey, I've got a header back OBX Racing exhaust system. 06' Tib 2.0 5-speed. I really like the system, noticable power increase, and a nice non-ricer sound. But at about 3500-4000rpms(most of the time in 3rd, 4th, or 5th gear) I get this terrible resonant sound. Trust me i can handle a loud exhaust but its deffinatly abnormal. I've dynomatted the trunk area and I've put iso-barriers between the body & muffler/tips to insure there is no contact between the two. It really puts a considerable amount of pressure on the ears. Any other RPM range it sounds kickin. Any help or pointers????