properly plumbed with a dual port wastegate closing off the adjustable valve prevents air from reaching the top of the gate and results in lowest boost
opening the valve allows air to reach the top of the gate and result is higher boost
but if the valve is closed fully it can also prevent air from escaping from the top of the gate and prevent the gate from opening which may result in overboost , i would make sure the top of the gate has a small hole (1/64 is fine) somewhere in a fitting between it and the regulator valve