The problem is obviously a restriction preventing the oil to drain back into the sump.

The Heath Robinson solution would be to fit an overflow pipe from the tappet cover to the sump (join up with the turbo's oil return pipe).

Don't ascribe to malice anything that can be adequately explained as stupidity!
Pajero LWB Gen1 3.2 Di-D TD Engine
33" Bridgestone D694s
2" Lift
Front Runner Rack