A resonator could help. Walker makes a few, some as cheap as $30 all the way up over $100. They work pretty well, I added one to a couple different exhausts I've had. I dunno how much quieter and without drone you can get, the Gibson is one of the quieter exhausts with really little drone. I met a guy at Summit Racing who has one and it was actually alot quieter than I thought it was going to be.