What's up Tyler! It's Cameron.To bring up an old thread, this is on an entirely different car however I have a bunch of rasp when I rev the crap outa my 04 bmw 330ci performance pkg. If I have read correctly shorter pipes welded onto my exhaust would cancel out the higher notes? or is this simply an rpm related fix? After aftermarket headers and deleting the cats my car sounds like crap when it revs, need to get the high frequency notes out of there. Thanks!
Look into the "rasp pipes" for the bimmers. I think using an inline resonator or inline perforated core muffler will help. It's not feasible to use Helmholtz resonators for higher frequencies on exhaust due to the miniscule size the tubes would have to be.