1993 Ford Ranger 93 Ranger odd idle and fluctuations

5 spd. Manual Ranger with high mileage. Only during damp weather, engine idles wildly, and almost feels like pedal is floored when driving. If I push in the clutch to shift, RPMs remain high, like throttle is stuck open. When I come to a stop, RPMs remain high (3-4k), then gradually come back down to idle speed. While sitting, idle speed will sometimes fluctuate up in the 3-4k range, but eventually returns to normal, but not below normal. "Check engine" light occasionally comes on while driving.

Diagnostic codes 0122 (throttle position sensor) and 0565 (CANP; cannister purge) were observed following one of these incidents. I've changed plugs, wires, cap, rotor, but symptoms persist in damp weather.

Could it be throttle position sensor? Vacuum leak? Thanks in advance.