Stock boost on a WRX is about 13.5-14psi. Wastegate pressure, which is a default condition where the wastegate is fully open all the time, is around 7psi at WOT (this is how the AccessPORT's economy map "controls" boost).

There is something wrong with the boost solenoid and/or the lines that control it. There's supposed to be a restrictor in the line, if that's gone, you'll run wg pressure. Sounds to me like somebody had an MBC on the car and didn't quite return it to "stock" right.