I want to modify my exhaust and thought of straight piping. Had a 97 12 valve that I straight piped no CAT and no Muffler and no issues, but in talking with some so called experts on the 2004 I have, I was told that I need to keep the CAT for back pressure? Not a mechanic by far but not sure what to do? Straight pipe no restrictions or CAT back no muffler? Not sure that does anything for me? Any help?

 

From what I have read here the cat is not very restrictive on these. I just removed the muffler and I am very happy with it.

 

Yeah I have been searching for info on the back pressure question with no luck. Was wondering what no back pressure versus some back pressure really affects with engine performance? I was told by a reliable source that it affects the performance of the engine and power so probably will just straight pipe 4" from CAT back less muffler.

 

O a turbo diesel there is no need for any backpressure. The turbo gives you all the backpressure the engine will ever need. I had my muffler off the 05 for 2 weeks and it was nice. I then lost my kitty some how, its way nicer now. Yea its louder but between that and the intake mods i did it way more responsive to the trottle now.

 

I put in a 40" x 4" straight through muffler after the CAT. Cool EGTs, nice sound, no drone, no complaints from the wife.

 

Thanks guys! Those that chose to go cat back why not eliminate the cat, other than to pass emissions if applicable? Anybody with stock truck and no cat have any issues with loss of power or need for adjustments to the wastegate?

 

I kept mine so I don't have to deal with putting it back on if I need to smog test. My understanding is the CAT makes no difference in HP provided you're way down in the 400 range like me. Also, my truck has never had any EGT issues so that was never a concern for me.