The MB test procedure is very strickt and must be followed step by step. You do not need to check current draw by idle speed air
valve. Just follow the procedure step by step and give me the feedback. It could be that your idle speed control valve is OK, but is not working because the ECU is operating in a fix mode. Most likely the ECU does not receive input from one of the following components; coolant temp sensor, air flow position sensor, throttle valve switch, OVP and O2 sensor. All of the components must be tested according to MB procedure before you start to replacing components. Otherwise it will be simply a very expansive guess work. Also before you start to play with Lambda setting, performance of all of the components must be evaluated according to MB procedure, including fuel pressure, and performance of fuel injectors. You have to be very methodical with it. Otherwise the whole work is nothing more then pissing in the wind.
Also, explain what DVM means. I can not find DVM in MB manual.