Need ID on this part under the hood

I have this whistling noise that eventially goes away that seems to be coming from this valve. First I thought it was a bearing like in the water pump or alternator but when I listened with a hose, it seems to come from this.
It's just to the top right of the windshield washer resouvor. It has the white plug going into it. Could this be making the noise
[img=http://img443.imageshack.us/img443/1694/p1150393lq4.th.jpg]

This part is a duty cycle purge solenoid.It will not only start to whistle,but after a while it will start making a knocking noise.The part will set you back $30.00

Well, I guess I can afford that. Thanks for your help,
Fred