MAF may not be the correct MB nomenclature, but there is a sensor unit that is located just below the air filter housing that incorporates a swinging flap or door. The flap position is measured and I beleive there is a thermo sensor device that measures air flow into the engine.

The fact that it appears your engine is starved for air would point to some severe restriction to it's flow. As has been stated earlier even a completely seized compressor would allow enough air into the engine to keep it running, maybe not enough for any speed or power but it would not stop the engine as you've described when you've had it runninng and tried to insert the crossover pipe. The fact that you where able to alter the EGR state pulling vacuum to it and that changes the running also leads to air startvation as a likely problem.

It hasn't been mentioned but I'll assume that the pipe from the valve cover to the intake snorkel is intact and not restricted? If it is restricted for some reason it would pressurize the crankcase and cause the shut-off solenoid on the IP to close the rack staving fuel and causing the engine to die. This condition can cause all kinds of weird running/dying of the engine, you press the accelerator the engine reves, pressure builds and the engine starts to die. It will return to a poor idle if you let off the accelerator. I notice you mentioned oil spray occuring, when there is a pressurized crankcase oil will spray in fime mist and droplets out from the oil fill cap past its gasket out onto and over the top of the engine and past the gasket around the pipe from the valve cover.