92 Daytona IROC with the 3.0 V6, automatic. Runs great for the first 5-8 minutes until the car reaches operating temperature. Then it stalls and stumbles upon pedal pressure and can only manage about 15 mph no mater how much you feather the throttle. New cap and wires. I didn't want to get into the mode of replacing parts until it resolves. I'm hoping this is a simple problem someone will recognize. Any ideas or suggestions much appreciated!

 

Unplug the O2 sensor, see if it runs any better.