1990 GT 5.0, manual, 240K. I've been chasing this problem for a long time. After a cold start up, it runs great and I can drive it around for a while. After a good warm up it starts to run badly - bouncing idle (600-800), stalls at idle, poor throttle response, trouble re-starting. If I let it cool down for about 15 minutes, I can restart and get a smooth idle again, until it warms back up. It seems to me like a bad sensor is coming into play as the computer switches modes from cold to warm. Any ideas before I throw more parts at it? So far I have: blocked off EGR, new throttle body, TPS, and Idle Air Controller, new plugs and wires, distributor cap and rotor, new MAF sensor, Coolant temp sensor, thermostat, ignition coil, PCV valve, O2 sensors. The computer was replaced some years ago.