DP is catted. If something fell off the catted part of the DP and got into the muffler, what is the remedy? New Exhaust or muffler?
Remove the muffler and see if you can shake any pieces out of it. If it is parts of the cat, then you'd probably want to remove the DP and clear out anything else that's left in there. Then you can put it all back, and should be fine.
But maybe get some data logs done to see what kind of AFR's you are seeing in boost. Sounds like you could be running hot (if you find out you are actually burning up the cat).