Buick Other

I have a 1990 buick lasaber, 3.8 liter, it is overheating, thermostat good, rad is hot on top but cool below, remover rad ran water through bottom of rad does not seem blocked, I am not loosing coolant, no coolant in oil, no white smoke, so headgasket seem fine, car is idling high, dont know y, cannot get gas/air mix correct, could this be cause of overheating. So can someone please give me an idea, have check with several mechanics, but cannot give me a definat answer, HELPPPPP : shock:
September 11, 2006.

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