Engine stalls when coming to a stop "not always"

1988 Chevrolet Celebrity, Automatic, 2 wheel drive 2.8 multiport V6. 86,000 original miles.
The engine stalls when coming to a stop in drive. (Sitting at a light it stalls out). When the engine is power braked at a stop light it does not stall. The IAC is new and has been set to specs. I have cleaned the throttle body, tuned the engine, checked the computer with a scanner, no codes present. I also checked the data stream and all the sensors are within voltage limit, etc. I just replaced the fuel pump, strainer, filter. Do you have any idea what could be causing the stalling?