I think the placement of the mufflers has a lot to do with the noise level on a split six exhaust system. I had glaspacs installed on my burb with Fentons close to the bend with long pipes after them. It was obnoxious. Sounded like a cropduster on the highway. I added another set near the end of the run and it is now mellow sounding. I think the aft set is really all I needed.