Muffler is deleted. Sounds great, classic Cummins sound upon take off, not obnoxious loud at all. No louder than stock between 35-60 mph with normal throttle input, just slightly louder in cab above that. Never gets too loud in cab with windows up, but sounds great resonating against objects.
BTW my truck has no factory piping left except the over the axle pipe and downpipe. OEM downpipe will probalby be next to get replaced.