The USUAL THREE bits of advice:
1. Verify fuel pressure at prime, and under load. If the engine won't run properly, use the bleeder valve on most fuel pressure testers to "load" the fuel system. Use a drain pan to catch the bled-off fuel. Consider replacing the fuel filter depending on mileage and condition, especially if the pressure is low.
2. Verify ALL normal "tune-up" items: Distributor cap and rotor, plug wires, spark plugs. Check initial ignition timing, and electronic advance. Assure the PCV, EGR, EVAP, and heated-air intake systems (including air filter) are working properly. Verify battery voltage, and charging voltage. O2 sensors get lazy with age, if it's got more than 50K miles on it, it's questionable. Even if the O2 sensor "works" it could be reacting too slowly. Make sure the ignition coil has enough power to reliably fire a spark-tester calibrated for HEI, and that is best done with the ignition coil hot from miles of run-time, and with the coil misted with water from a squirt-bottle. A plugged catalyst (or other severe exhaust restriction) can stall an engine--check for back-pressure problems.
3. Connect a scan tool, verify EVERY sensor and computer output. Look at the fuel trim numbers. I'd be paying special attention to the coolant temp sensor, the TPS, and the IAC. You can check for "codes", but the real diagnostic power is in the data stream.