Did you replace both hoses (from the fuel distributor to the idle control valve, and from idle control valve to manifold)? Mine were rock hard and loose on the nipples, causing serious air leaks. This can cause stalling.
Check all the other vacuum line rubber connectors, especially the line to the control unit on the fender -- leaks here can screw up the mixture control, causing either over rich or over lean idle. Most of the rubber bits are shot by now. I replaced all of them -- cured hard shift problems at the same time.
Also, did you clean the idle control valve -- you can just take it off and spray in some carb cleaner, shake with a thumb or some such over the holes, then dump the carb cleaner, repeating until no more crud or color comes out. The idle valve, when dirty, will stick closed, causing the car to stall. Can also cause rough idle as it jerks rather than moves smoothly to control idle speed. I've not cleaned mine, but will soon, as Mom is complaining about stalling with the AC on.
If this doesn't fix it, get the idle mixture checked -- if it was set with leaking hoses, it is now too rich.
If that is OK, then the OVP relay is a likely culprit -- causes stalling by killing the voltage to the mixture control circuit.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!