I have the 400 fitted with LBMs, 2.5 downs into x pipe and then into 2.5in DynoMax UltaFlow weldeds out dumps in front of the axle. The pypes site said 8.5/9 out of 10 in loudness. Some of the best flowing muffs out there(why I chose them). Advised not to get them if you have touchy neighbors. They would probably be within reason if I had tailpipes.