Will this set off any codes on a 2004 lly? I got the down pipe(no cat) 4" back single

Tough to say. Some get'em and some dont. I never did with my 04 with an MBRP turbo back system. You'll love the sound...You might get lucky...

It didn't on mine. You should be fine and love the sound.

Thanks guys, just got the diesel and I am lovin it. So many options and so many different things to do to these trucks.