I was under my truck today installing gauges and took a good long look at my downpipe. I have heard a lot on here about how the stock downpipe is junk and all of that because it is so restrictive. I have to tell you, mine looked very smooth. No ripples, no kinking, and no foil stuff on it to hide the ripple/kink... Also, it looks like a 3.5" pipe to me. Oh yeah, 04 PSD CC 4x4 bought new one and a half months ago. I am getting ready to order my exhaust and am seriously considering just the cat back after looking at the downpipe. What do you guys think, did I miss something?

 

I am inclined to think leave it alone. I have an 03. Mine is covered with insulation for sound attenuation and heat. I don't see that if yours is not restricted, don't fix it. The 6.0 PCM is looking for back pressure.

 

Mine is also a pretty good pipe & no insulation. I'm going cat back for that among other reasons. One other reason is that the cat itself is 3.x" pipe connections. So anything pre-cat will have to reduce to fit it. I may add the downpipe later, but for now this seems reasonable. My build date is 6/04, so perhaps the downpipes got better with the later 04s.