I am convinced that no independent mechanic in my area (CT) knows the 16V's enough to service the idle and start/stall problems. Don't change your air flow potentiometer unless you and everyone is convinced it is causing your current problems. I made the mistake of believing my independent mechanic and paid for a new air flow sensor potentiometer assembly and I am back to square one. My start/stall and idle problems persist. It was a costly, and ultimately useless, repair -- not to mention wasted time and money.
Since my last posting, the "vacuum leak" problem has been taken care of (hoses and clamps) as suggested by MBDoc and Richard through the forum. My own dealer said they don't have a mechanic who's trained on this 16V engine so they won't touch the start/stall and idle problem. Another independent mechanic (Porche specialist) suggested the onboard computer has to be replaced (that's over $1K); so for now, I am just living with the nuisance of start/stall and high idle (1400rpm).
1987 190E 2.3-16