Audi Repair: differential pressure regulator, mass air flow sensor, mass air flow

Question
Jan, I'm writing back on the idle control valve, could it be the differential pressure regulator. when we plug the electrical unit in, off the regulator my car wont start. when unplugged it starts, but takes awhile to get it to idle. and backfires when you shift or let off the gas. thanks

Answer
Where do you see the differential pressure regulator?  If you have an idling problem, I would suspect either the idle control module, or the MAF.  If it backfires when shifting, then there is still fuel being supplied when the airflow is low, indicating you may well have a faulty Mass Air-Flow Sensor or MAF...  Let me know what you find,  Jan