going to do a dpf delete with economy tune within the next few weeks have all the parts to do it ,truck has a few more trips to dealer to fix a few things first , wanted to know just how resrtictive the cat is ,i was thinking of leaving it in for the queitness but dont wont to defeat the purpose of the dpf delete and economy tune if the cat is going to cost me mpg and performance if i leave it in ,has any body compared mpg with it in and ,thanks any input app thanks

The cat sucks too,if your going with the dpf delete can the cat.If you want to keep the muffler it is not nearly as restrictive as the dpf or cat.

so does it hurt performance or mpg ?

Check this post I just did. May help.

http://www.dieselplace.com/forum/showthread.php?t=387546

On page 3 this section.

Yes it does.

This might be a dumb question but Im not in a position to look at any duramax's.

I ordered my DPF delete and I have already done a DPF back exhaust on my 08, will I still have the DOC on my truck after I do the DPF??? And if I do what part will I need to get rid of it? Thanks for your help.