To answer your last question, first:
It is very important that you have NO air leaks, anywhere, period.
Buy and install a new complete flame trap "kit" from FCP Groton. Install all the items in the kit. It's not that expensive.

The IAC or CIS or whatever everybody else is calling the thing this month:
As has already been stated, the working (moving) part is in the portion where the two hose ends connect. It's, for lack of a better term, a "flapper" or a rotating "door" that is activated by the closure of the Idle Switch that is located on your Throttle Body and attached to your throttle "flapper" (the butterfly valve) that is actuated by your throttle. When the Idle Switch closes, it activates the IAC valve, allowing this IAC valve to open or close according to the load imposed on the idling engine by such factors as whether you have your air conditioning turned on or off.
Clean the Idle Air Control valve with carb cleaner, throughly.
I remove and clean mine every other oil change, along with removing the Throttle Body and cleaning the throttle butterfly (attempt not to introduce any carb cleaner into the Idle Switch). I also remove the flame trap and clean it at this time.
Maintenance is not ONLY changing the oil on a regular basis, and frequently.

Larry Payne, MSME
ASME, ASHRAE, SAE
2 ea. 1986 245's, 1 1991 244. 220,000 - 285,000 - 111,000 respectively