I have a 93 WRX, and having used the Search engine regarding this Topic I understand that the Boost Control Solenoids have a tendancey to be noisey.

Having just tried a New solenoid and finding it to be exactly the same I tend to agree.

But a question that I do have, is should you be able to hear the Air being pulsed by the solenoid. I know that the solenoid itself may make a ticking noise, but should you be able to hear the sucking air being pulsed (i.e a high speed Hiss...Hiss...Hiss in time with the solenoid pules.....this is very difficult to describe in words as you might of guessed).

I have checked all pipework in and around the Solenoid and throttle assembley and can find no sign of a leak.

Once again it's probably normal and I'm just paranoid....

But I'm certainly going to wrap some sort of sound insulation around the solenoid as it's starting to wind me up.