In my 190E 2,3 8v i have got a similar problem as you John. I know the engines arent' the same but here are few thing I noticed.
-Warmup stage is not notable. I have got same rpm regardless engine temp and outside temp.
-When the engine stall(no misfire) the tach drops very quickly. Engine catches and stalls for 2-3 times and then it runs fine again. Sometimes for days, sometimes for months. Could a fuel pump with insuffient delivery cause this? Then during stalling the pump gets time to pressurize system again and give enough pressure for injectors to open normally. Just my thoughts...
-During normal conditions there is a vacum pressure in the fuel tank. How would a clogged charcoal canister affect fuel delivery?
-When enginge starts again I hear the pop sound from the cat as described by John
I had also a very worn ground wire between engine and chassi. Grounding point at the high voltage capasitor and intake manifold on engine. After I did replace this wire with a new one the stalling occur more often? Could it be just a coinsidence?
'87 MBenz 190E 2,3 8vlv