Yes mine has the Bisson Pitts muffler but it isnt modified in any way. The only thing I've dont to it is plug the hole for smoke as I dont have a smoke system on it. This muffler allows plenty of performance but is very quiet buy most standards but still gives it that throaty sound of a BIG engine. I like it & plan to go with the same muffler on the new one I purchased for the Katana. I wouldnt see any need in modifying it for any reason.