1984 camaro z28 H.O. original parts

Every morning when I start the car it idles at 1500-2000 rpms in park. In drive while holding down the brake pedal it idles at 800-1000 rpms. It leads to the engine doing a run over(Engine tries to keep running when turned off).

Ive learned that if i let it warm up then cool it down, warm up then cool it down, and even sometimes doing it for a third time before it idles down to 500-600 rpms.

Ive recently been given a manual and would like help narrowing it down.

Ive had the idle speed changed by a mechanic

My car doesnt run extremely hot. I had a 160* thermostat in over summer and kept it around 170. Plan to switch to a 180* thermo for the cooler weather until i put it away for the winter.

The only other two options is the electric solenoid and an incorrect ignition timing. I dont know what either does.

If im correct the electric solenoid is what makes the idle drop after it warms up?

The mechanic said the electric choke, which im assuming is the electric solenoid, was broke and that he fixed it. However I didnt see a bill for a new electric choke.

Another thing to add is the choke light went out( When I have the key turned to on but not all the way) when it began to idle too high for too long.

Can anyone help?