Apexi N1 Exhaust Hitting Bottom of Car?

[red93R1]

This might be border line tech question, but ever since I installed my catback exhaust (Apexi N1 Single) the exhaust has been hitting the bottom of my car. Actually right under my seat it causes to vibrate at certain RPM's. I looked under and it was hitting one of the bolts that holds down the seat. So, I shaved that up a bit so it's not hitting that anymore feels better, but it's still hitting the underbody down there. I've gotten new rubber hangers and put those on, but still no change. Just wondering if any of you guys have experieced this before especially with the wider diameter exhausts. and if there's anything you've done to fix it...Oh, on a S13 chassis w/ red-top.

Thanks