Hunting for idle/whistling at idle

[PlayingWithTBI]

I know on a TBI, the IAC can whistle at times. I wonder if a Vortec will too. I wonder if it's a result of "hunting for idle" and not the cause.

 

[GoToGuy]

Didn't catch if you noticed , does the noise follow in step with engine rpm ? Or change of rpm off idle , just stops, as in doesn't follow rpm?