are idle control valves known to rattle?

[Bebbetufs]

I have a rattle from the throttle body area or the top of the engine. It is mostly heard around 2200 rpm and mostly when coasting, when the throttle is quite closed. The noise can be "adjusted" via the throttle pedal. Since the butterfly valve has no slop the most likely cause is the ICV. The idle is steady and the valve and passage has recently been cleaned. Are they a known source of noise?