If its the slash cut "mufflers" theres not a whole lot that can be done. When i had mine i put in as much fiberglass packing as i could and put in voodoos speakeasys. Both helped with dropping noise a little, and i mean a very little. The tone was much improved but still loud as hell. Putting some Holeshot mufflers on the UFO pipe was the best way ive found to quiet down a Ufo system.