Who said you could apply logic to the situation?!?!?!

No, really....it is logical, follow my reasoning; there is a method to my madness.

The only components that can affect your temperature gauge the way that you spoke of are the thermostat, and the engine cooling fan. Your engine cooling fan is a two stage fan, meaning under normal circumstances, it will turn on at the lower speed whenever a certain temperature is reached, or the air conditioning is turned on. Once a certain temperature is reached, AND you turn on the air conditioner, it kicks into the higher speed. Of course as you are heading down the road, at higher speeds, the outside temp sensor will alert the climate control that the front fan is no longer needed, unless this signal is overridden by the ECT. So, really, I guess the problem could be the outside temp sensor for the climate control, but...

didn't you also say something about running rich? or am I confusing you with someone else I attempted to answer? Either way, both of these parts are cheap...both of these parts could do what you are saying...the ball is in your court.

Chris