I have been driving a 1997 Dodge 2500 W/ Cummins, 5spd. since 1997. I removed the muffler in 1998, not too loud, I gained 4MPG and it sounds great! There are Shorty mufflers or a Resonator that can be installed in an M818 instead of original muffler at a much cheaper price, like $36.00. A Cummins with a LONG strait pipe sounds great, as long as it is Behind you. I make my Stacks from used Drive shafts. Solid material, and easy to weld. Phil