I want to delete my dpf/cat, I ordered a tune and flashzilla from tunezilla, but I have a few unknowns.

Can I just gut the cat right behind the turbo and the dpf further downstream?

Do I have to clear all fault codes before I flash it?

I have some codes I clear, but the same ones show as pending and I can’t clear the pending codes so they just come back.

Any help is greatly appreciated.