This is Prodrive's 3-Port Boost Control Solenoid. When tuning with afterket engine management, this will allow you to take control, and raise the factory boost level. The Subaru Factory Boost Control Solenoid is not capable of handling high boost pressures, and will become uncontrollable at higher pressure. This is controlled by any aftermarket engine management that allows you to set wastegate duty cycle. Please note that tuning is required with this item.