[mwebb]

the runaway issue is not ever going to be an issue for your engine
with 1 0z per 6500miles

boost bled into crankcase is not a good idea ,
(1 bar of boost can pop out the rear crankshaft oil seal - ask me how i know that )
you could use a check valve to allow flow when boost is not present
like a
crankcase vent valve / PCV valve -

and the newer TDi dumps the oil back into the crankcase after the cyclone portion of the crankcase vent valve so no nastiness ends up wasted , it all gets sent to the combustion chamber
to be
combusted ...
so

PCV "catch can"
no engine should ever need a PCV Catch can , if yours does , that is one indication that your engine has bad piston rings or a sloppy seal at the turbo center bearing
or
the piston rings may just be frozen with carbon in the lands because the engine has been operated with
poor quality oil for many moons

(you can use VW 507 oil in that engine)

so
stop using poor quality oil ,
identify the problem (s) and repair it (them) , which will
improve your fuel economy and make the use of a PCV Catch can
UN necessary / irrelevant

having said that
i know many posters on this forum are on the balls of their butt
financially ... and have no disposable funds to be used to repair those problems ...
if that applies - a catch can is still a bad idea