I guess I didnt understand your opening post. The only time I consider anything sticking with regard to throttle bodies is if the throttle blade actually physically sticks in the TB bore. Now are you referring to a hanging idle (or one slow to return to the base setting) as sticking? I think so.
A vac leak often has to be huge to hear any hissing - many of them are very quiet indeed.
The reason I asked the questions I did in my first post is that if it happens while rolling, it's by design. If not: If you disconnect the IAC and rev it up a little and let it return to idle, does it hang? Of course, dont drive with the IAC disconnected, as your car might stall.
I'd also note that much of the info in Jrichker's idle surge sticky can apply to your issue. Might be worth perusing the thread.
I 2nd the vacuum leak theory. Hook up a vacuum gauge to the motor while its running. A hunting needle between 14-18 hg usually indicates a vacuum leak.