Somebody already said that the noise can be confused with a TOB noise. This is what happened to me.
My clutch went at 20k miles on a 08 WRX. Replaced with Exedy OEM and the noise started less than a week after. The TOB was replaced again, the noise still there. Then we installed a TSK3 kit and the noise came back.
Yesterday, I removed one of the IC brackets to be able to play with the fork while the car was idling. The noise goes away as soon as any pressure is applied to the fork. No matter in which direction, to the front, the back or the sides. So the noise is a vibration from the fork.