There are 2 ways to start these engines.
Cold - turn the key and at the first couple of explosions press the accelerator.
Warm - turn the key with the accelerator 1/2 way down (more or less).
This is actually from the MB manual.
If the problem is with the Warm Running Device. The AAV has an air filter mounted sideways that you can unscrew easily. When the engine is stalling check to see if there is any suction there. If there is it's not good. With engine cold there should be strong suction there (to the point that if you close it with your finger the engine will stall) and it should disappear completely in a couple of minutes. May not be a bad idea to unscrew the WRD, separate the thermostat part, check it for extension in hot water, disassemble the AAV to make sure everything is sliding well there.
At idle separate the IP rod from the crossover shaft. Push down about 1/4" on the rod, if the rpm increases your idle is lean. Turn the IP idle screw 2-3 clicks CW (WITH ENGINE OFF you have to push the knob until it seats into a screw slot) and see if it improves. Now push the crossover shaft 1/4". If the rpm increases your idle is rich. Turn the IP idle screw 2-3 clicks CCW. You can check the plugs color but that would be an overall mixture indication (mostly driving), white-lean, brown-OK, black-rich.
When stalling you can also try to adjust the manifold idle screw. If it makes no difference then it is clearly lean.
Forgot your original question:
There is only one idle screw and it is located on the intake manifold very close to the cylinder head and to the front of the engine (see first pic).
The IP idle screw is only for idle mixture adjustment (second pic).