Oldsmobile/Buick Repair: low speed engine stall, driving a stick shift, bbl carb

Question
1987 Buick Regal 305/307 c.i.d 8 cyl. 4 bbl carb.
103,000 mi.
I am the original owner. Of late the engine will stall at idle or very slow speed, such as slowing to a stop or to turn a corner.It will usually restart immediatly or after a few minutes.There is no frequency pattern, some time it will stall 2-3-4 times in a day,then won't stall for days.It seems to be fuel related. I have changed the fuel pump, fuel filter,and gas cap all to no avail.Other than that the car runs strong, starts easily, burns no oil. A minor tune was performed 20,000 mi ago but no carb work has ever been done.I'm perplexed.

Answer
I am going on vacation so I hope this helps,
Surely since its a car-borated engine with numerous vacuum lines, one vacuum line could be leaking causing this condition.
 Setting that aside for now you could have a skewed T.C.C. valve. Thats the transmission converter clutch valve. It locks up the transmission torque converter to aid in fuel mileage at speeds above around 40 mph. The unit is normally locked out of 1st gear. When it acts up it applies at the higher speeds but doesn't disengaged. This will cause the engine to stall. The feeling to the driver is quite distinctive. The normally is a shaking or vibration felt the moment before the engine stalls, it could feel like a shutter not unlike the sensation one feels when driving a stick shift and comes to a stop in gear without depressing the clutch petal. The hole thing is controlled by the engine computer. There is a connector on the transmission which is normally square with 4 receptacles, disconnect it and drive the car as you normally would. See if it stops stalling. If so you need to replace the solenoid. Its located in the transmission under the transmission pan. This a long shot but without inspecting all the vacuum lines and numerous other sup-systems its well worth looking at a could be a fast test. Just unplug it and drive it normally... John