Yep all that oil down the exhaust no good for the DPF. Although I bet the turbo was nicely lubricated from the inside out.

I know Roll Guy had a post a while back about Liqui moly product that cleans DPFs.

You won’t be able to gut the DPF, the computer is too smart for its own good, and it will trip a code from the delta P sensor across the DPF (for the lack of any delta P from the gutted DPF).

Edit: I didn’t read your post carefully, you said the back pressure was after the DPF.

In that case I would drop the exhaust pipe post DPF and see how your pressures and temperatures look. If things go back to normal then you have a plugged muffler which should be easy enough to replace and much less expensive than a DPF $$$$

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech