I'm sure it's the headers with the resonator. Get a longer quieter res. and you should be ok. What that res. is I don't know. Preformance comes at the price of louder free flowing exhaust. Maybe Dynomat the trunk. Bet that would help a lot. Or get a Borla. That should be just right. Too bad they are rare and eleventy billion $$$. Maybe a 3rd muffler in place of the res.?