I don't understand what you mean by "gunk", either. Have you examined closely the oil drained from the pan? Have you tried inserting a "borescope" camera into pan thru the drain plug hole? Maybe someone left a shop towel in the engine before they buttoned it up. I've seen that happen, and heard of it happening on someone else's engine. I think I'd pour clean diesel into the top and drain it out the bottom. It's super cheap, a good solvent, and yet still a lubricant. That way you could readily see what "gunk" you really have. Like I suggested before, pull the filter and blow comprested air thru the filter adapter hole. You'll hear bubbles in the diesel in the sump. If any "gunk" is in the pickup, it should be dislodged. Drain again, examine again. Cut the filter open carefully, and closely examine the contents. If there is any metal particles in the filter, you may have significant damage.
