The large diameter hose that feeds the TurboCharger is the Intake from the
Air Cleaner Housing.(It has the smaller diameter Valve Cover Vent hose running
into it in a "T" Upstream of the Turbocharger.)The Turbocharger when the engine
has any RPMs on it produces LARGE Suction on BOTH those hoses.

The Oily Mist and Crankcase/Valvetrain PRESSURE being Vented out the Little
1mm orifice on the side of the Valve cover is PROOF of Excess "Blowby".
Something is putting SO MUCH PRESSURE inside the Valve cover (or the top-
of -Valve Cover Vent hose system is Block[ing]ed) that it's OVERCOMING the
Turbocharger's SUCTION.
('Called a MB Shop Foreman and described your symptoms to him.)

Since you're only experiencing the "Venting" along with rough running the excess Pressure MAY be attributable to Valve Stem Seal problems.
Or some
problem with the Valve Train which is allowing the Cylinder Pressure direct
access to the Valve Cover.If it's on the Exhaust Valve side the incomplete
combustion would lend itself to the "Stinky Exhaust".I'm going out on a limb
and Prognosticate it's an Intake Valve Problem...Bad Seal...It sucks in Oil
from the Valve Cover Lube System...Incomplete Combustion and Oily Exhaust.
OR it may be Both at the same time.

Hell, it could be one or more bad rings.
You need more Diagnostic Info.

Try the "Loosen the capnuts (One at a Time) on top of the injectors trick"
to try and narrow down WHICH cylinder's Valve Stem Seal(or Whatever) is bad.

I'm almost sure a Cylinder Leak Down Test will tell you everything you want
to know.

Oh Yeah,your only Easy Fix option is if the Top of Valve Cover Vent Line
(that runs from the 90 degree plastico fixture in the top of the Valve Cover
to the accordian Tube feeding the Turbocharger) is stopped up.So Check it,FIRST!

__________________
'84 300SD sold
124.128