High Oil Consumption: Causes & Solutions

Hello, I need your help.
I recently bought a 1993 T4 with a 1.9L TD engine, and I haven't been very happy with it so far. Initially, the car was very difficult to start and produced a lot of smoke, to the point where the fire department almost got involved. My mechanic inspected the engine and concluded that the electronic fuel injection system (ESP) was faulty. The ESP was rebuilt, but the problem reappeared after 100 km. A worn gear was found, which was causing the timing to be incorrect (the ESP may not have been broken in the first place). The van is running now, but it's consuming a lot of oil, or to put it another way, the diesel is burning with the oil. After 100 km, 2 liters of oil are used. My mechanic now believes the problem is either with the valve stem seals or the oil scraper rings.
My question: Could such high fuel consumption be caused by this? The compression is 30 bar in all four cylinders.

Is it possible that the turbocharger is about to fail and that oil is leaking into the combustion chamber through the turbine shaft?
Just make sure this thing doesn't become a "runaway" situation!

Greetings.

Hmm... if the compression is that good, it's probably not the engine itself. Give your 'mechanic' a hint and suggest they check the turbocharger. I think that's the problem!
'Two liters passing through the valve stem seals would be a world record. It also can't be the wiper rings, because otherwise the compression would also be reduced or uneven.'

... a little reading material to go with it:

Okay, I'm ready. Please provide the German text you want me to translate.

Thank you for the prompt information. I will pass this suggestion on to my mechanic. Thank you!