Both my 91 420SEL and 85 380SL were having the usual stalling issues. They drove fine but when I was comming to a stop the RPM's would drop below 400 sometimes it recovered and other times it stalled. Hot, cold A/C on or off it didn't seem to matter. I'd say it stalled between 10 and 50 times a week.
One day I went for a ride iin a friends Audi RS 4 wagon (oh my what a car!)When we stopped for fuel he put in the 103 octane and we had a long conversation about fuel quality effecting performance blah,blah,blah. Finally I put in 1/3 a tank of racing fuel mixed with 2/3 91 the car ran great and the stalling all but ceased at the next fill up I put 1/4 tank 100 octane with 3/4 91 occtane. That was 2 months ago since then I have been running 91 occtane and the stalling problem is 99.99 percent gone.
Just my experience