A straight piped Cummins sounds badass! A friend of mine out in PA has a Dodge 2500 wih the 24v Cummins. He got sick of the stock exhaust and want to put stacks on it, but no money for now. So instead he just cut all the stock muffler and cat(?) off and finished it off with a piece of 4" or 5" pipe with a turnout just behind the door. And whle driving, it isn't een that loud inside!