If you had the head off it is possible that the engine temp. sensor could have been damaged. Cooling system cleaners can also cause damage to these little sensors. A bad sensor can cause the problem you describe. I would check the resistance of both engine and air temp. sensors at known temps. and compare to specs. Also check for a vacume tight seal on your map sensor. These three sensors can cause all kinds of mystery problems. Sometime when you replace the temp sensors the small variation from one to another even though withen specs can cause a lean or rich condition if both new sensors are off a little in th same direction. The factory tuned the map sensor to perfectly match the other sensors in the car. If your map sensor has screws and not rivets and you are very good with repairs and you understand the workings of a variable vacume actuated induction coil you can repair and adjust it. I have done it succesfully.

Thad
Seattle