82 prelude high-idle

for idle problems i would suggest first, check for intake vacuum leaks, and make sure the PCV valve is working properly

then if the idle problem persists but only when the engine is cold, it's ignition

but if the idle problem persists even when the egine is warm, it's the fuel system

since you get good mileage, i think the carb's choke didn't get stuck closed. In fact, i think your carb is fine.

and that the idle races up and comes down indicates a major vacuum leak, most likely a stuck open PCV valve. You won't be able to tell if a PCV valve is stuck open when driving, it's supposed to be open on moderate and wide open throttle anyways. But the problem is pronounced when the throtle plate is closed