OK, I checked it. There is more black grime on various parts of the 06 engine than there is on the 05. When I pulled back the black plastic mesh from the charge air hose (? the large top hose that looks like a radiator hose?) it was very slimy - it looked almost like it was sweating. Could this be the source of all the under the hood grime and thus air filter particulate? Perhaps somehow there is atomized particulate floating around under there?

All that blowby oil, plus outlet compressor temps easily approach 300* at 15psi Boost - pull the hoses, clean with hot soapy water, rinse with hot water, blow-dry with the vacuum cleaner - clean the compressor outlet, c-a cooler hose connection, etc, so no more oily surfaces - check the CCV inlet port right at the turbo inlet - look for anyplace that is leaking crankcase blowby, from the CCV puck to the turbo hoses to the c-a cooler - even loose oil filler tube cap - these 4cyl Diesels generate a lotta blowby from having only two combustion events per crank revolution - that's why you never see passenger car 4cyl Diesels much over 1.9L, too difficult to control emissions from such violence - at 2.8L, we got a monster, and you'd know it if it weren't for the twin balance shafts and the liquid filled motor supports and the AFC valve - you oughtta sit in a late GM suburban with a transplanted 3.9L Cummins 4cyl at idle................