If you are talking about the factory boost solonoid, it is bolted to the front of the passenger strut tower with 2 black rubber hoses coming out of it towards the drivers side. If you have a look down at the wastegate actuator (connected to the front of the turbo), follow the hose coming from this and you will come to a t piece with one coming from the intercooler piping and the other going to the boost solonoid.
Hope that helps
Jeff.