Oil not draining but going past seals

[audi660]

I've had 2 different rs2 turbos on my urs6 and both of them are pushing the oil past the seals and not draining fast enough to the sump. I've even reduced the supply feed to 1.5mm and there is no difference. My car smokes until I clean out the boost pipe going to the intercooler and also the intercooler. Then there is no smoke for a while. The car has stock oil feed and return hoses. I don't know what to do anymore. Please can someone assist me with some info? Thanks so much

[sal_s2]

Check that the return pipe isnt blocked

[newsh]

There's a small one-way valve between the inlet manifold and the PCV pipework. In the S2 its below and forward of the throttle body, it looks like two pipes of different sizes joined together, about 20mm and 30mm diameter, the valve is hidden inside that joint. The valve is there to apply vacuum to the crankcase when the throttle is closed.
If the valve diaphragm splits or sticks open the boost pressure in the inlet manifold gets passed to the crankcase which will blow oil past the turbo seals.
Worth checking.