I doubt it. Probably just a convienent place to vent the pump without venting to the atmosphere. In 1981 (when they went to the piston pump) they decided to vent the pump directly into the crankcase instead of the intake. Don't know if this is why, but if the diaphragm tears on the intake vented type, the pump can actually pump oil directly into the intake from the the crankcase. If this happens, the car will run rough, and the engine may not shut off as the engine will actually run on pure oil instead of diesel, believe it or not. Makes one heck of a smoke screen when that happens.

I know that VW diesels, especially the 1.5s, can run away if the rings or vale stems are too worn, so it's certainly believable. I wondering if venting it into the crankcase instead of the intake had something to do w/ the going from a pneumatic governed pump to a mechanical governed pump... Were the OM615/616s just bored/stroked versions of the OM621? Googling shows a lot of part interchanges.

Edit- Forum search indicates they're more or less the same engine.

Mercedes was still venting into the intake, or more specificly the air cleaner, on the newer W123 cars. These cars no longer used the pneumatic governor.

Forget K&N filters,they are designed to remove money from the wallets of the gullible,not dirt from the air. Your oil bath is a superior system which is still used on heavy Diesels to protect them.