W221 3.5 petrol Misfire at idle?? Had new coils

[Uncle Benz]

I thought that …. but certain fault codes on my w221 specifically call out that it doesn't seem to cut the offending cyl. Coil packs being a good (poor) example ….

P301 misfire damages TWC (when you look up TWC its the CAT)

Yes, it’s warning you that damage to the three-way converter (catalyst) can occur because of the misfire. It’s rare it actually gets damaged, but unburned fuel getting through to it can melt the brick.