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.

I would contact the manufacturer of the tune about the codes. As far as the exhaust, you could gut it I suppose, or you could get a custom pipe made and install it and then save the original stuff intact in case you ever want to re-install it or sell the car. Just my .02. Most tunes are labeled for off-road use only BTW, so there is that........

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)