Thanks for your input - and yes you got me right. I will check the oil vapor recovery system with the excellent motivation that it is simple in relation to strip down the engine.

One comment to the logic train of thoughts; combustion pressure blow by will build back pressure to the turbo oil return through the crankcase, which is the same as blocking the return, which was one of the two reasons the turbo provider listed as a direct reason for the turbo to leak extensively to both compressor and turbine. Both have been oil filled, with the difference that the turbine housing vaporizes, spit out, or "coxes" the oil, while the compressor leads it to the lowest and coolest point in the system.