Did the best I could to check for vacuum leaks. Couldn't find any. I took the pickup for a spin. It behaved normally. Only when it's idling does it lope/high idle. What sensor is it that triggers the engine loping when the there's air in the cooling system? It's not the ECTS, is it?

I also made sure, just for my own peace of mind, that there was no exhaust getting into the cooling system. That is the reason I had to tear the top end apart again after only 5,000 miles.