Hi again,
I'm pretty sure the IAC on mine needs cleaning out. It'd appear, since it sits on the underside of the Throttle Chamber, you have to remove the Throttle Chamber, so I've got gaskets (and some time) coming.

Once I get to it, is there any way to test it ? Maybe run a voltage to one of its wires (I'm guessing it just moves a 'valve' to open outside air into the plenum) ?

My car is a hard start when cold (no CE lights, no obvious vacuum leaks, and just did 02s). Once warm is no problem. Also, when cold the car shakes and RPM's drop - just like a carb'd car with no choke would do... I'm sure I need to get to it and attempt cleaning it out. I guess I just spray some Carb Cleaner in the main square hole on its top ? Maybe in a vacuum line ?
Didn't notice anyway to get to the actual valve by looking at the pic on subaruparts.com

Thanks for any advice on testing it !