I have a 2000 2500 Cummins. I'm considering just taking the muffler and the cat off and just running a straight 4 with a 5" tip. I was wondering if this would impact the overall performance of the truck or harm anything??

 

your EGT's would go down about 100F, plus it would sound like a peterbuilt

 

you will love the bigrig sound and your turbo might spool a little quicker.