Dave:

Dollar to a doughnut the valve guides were reamed for "clearance" and are now too large for the valves. It is never necessary to ream an MB guide to fit -- they are correct from the factory (unless defective).

The other posibility is incorrectly installed valve guide seals -- I'm not sure if they are the same size for intake and exhaust or not, but if switched, might leak. They could also not be snapped down completely or damaged during installation, also. Quite a bit of oil will go down the guides if the seals are bad -- even on a diesel, especially at idle, when there is some vacuum in the intake.

Unfortunately this means disassembly or ignoring the problem!

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!