94 sc2 keeps dying

I have 1994 sc2 coupe, twin cam with 139,000 miles. After driving for about 20 minutes, the car dies and is hard to start again. It happens more frequently on warm days and less when I haven't driven It for a few days. It happens on the freeway, back road, parking lot, but mostly at night in downtown Detriot. It has been in various shops over the last 6 months and no one can find the problem. I was getting codes 19 and 42. Replaced the o2 sensor, crank position sensor, ignition module and coils. It still does the same thing. Now I get code 19 only. Any ideas befor I spend $300.00 on a PCM? I hate to put another $300 into a $1000.00 car. This is the first time we have had any trouble with the car;sans the wipers coming off the motor constantly. --more on that another time, I fixed it permanantly.
Thanks
Mark
94 sc2 coupe
72 914 V8

Coolant temp sensor, throttle position sensor, idle air control valve, or map sensor are all possibilities.