3.4 idle speed too low - sometimes

I have a 1995 T100 with the 3.4 V6/auto trans. 320,000 miles. This
weekend, I noticed that occasionally when I started the truck, the idle
would drop to probably 250-300 RPM as indicated on the tach. It only
did it after the engine had warmed up, and even then not all the time.
The engine still ran smooth and would accelerate fine, but the power
steering didn't work well bc of the slow idle speed.
It seems to come and go.
I know the obvious place to look would be the Idle Air Control motor.
But does any other sensor or device have a direct bearing on idle
speed? The engine runs well otherwise.

Thanks everyone.