that's exactly my thinking and here is what I found in DIYautotune FAQ

"Idle Air Control valves versus Fast Idle Valves--- What does my car have and how can I tell?
Here's a way to figure it out-- on a cold morning, when you start your car it idles higher than normal right? That's because this valve is open letting more air in to idle the car up to it warms up faster. Now... if you sit there until it warms up, does the idle drop back down to normal all of a sudden? If so it's a FIDLE valve (two wires, ground and 12v+). Or does it slowly idle back down to normal a little at a time? If so it's either a PWM or stepper motor valve. ..."

Efi owners with this kind of valve tell me please how it behaves on your car? As I didn't have the chance to experience it...