On my 06 I removed the rear beauty cover and drilled nine 1/2" holes in the rear baffle plate and five in the front baffle plate, deep inside (took a long drill bit). I painted the ends with hi temp black paint and left the beauty covers off but reinstalled the screws. Its looks ok to me and sounds great. No popping, backfiring or ignition changes. No loss of power either, just a nice low growl at idle that increases nicely at the turn of my wrist.