my '90 F150 is exhibiting similar behavior. Were you able to get it fixed? I is puzzling to me. No one has been able to give me a reasonable explaination to fix it's behavior. It starts fine, but can run REALLY rough until it gets warm. Similarly, like it is flooded. Off idle doesn't seem to help very much. Sometimes, it doesn't have issues. It may need plugs, wires, distributor, etc. But it does not explain this senario. AND when it does warm up - it's fine. Again, it starts fine from stone cold, and runs well when warmed up. It's the 3-20/30 minutes that the vehicle is undrivable.