My friend had a full race kit (ecm, header, muffler) on his 03 XB9R. He bought an econo-drummer (xb12 muffler, dual exits) and it sounded much better. It was one of the best sounding bikes out there.
I got my hands on a used drummer with the billet end cap. It doesn't sound nearly as good on my 08 XB12R. What gives?