The wastegate is set at a certin pressure at that pressure it starts to open blowing off if you will the extra pressure I am assuming its an external waste because of the b-1 but I maybe wrong if not then it should probably dump to your down pipe??? This opening allows the extra pressure somewhere to vent instead of going through the turbo thus lowering the turbo pressure.

 

Putting a wastegate on is going to extend the flow capability of the turbo when the turbo is reaching the max boost setting (set by the wastegate actuator). the gate is merely a valve that opens to reduce backpressure when the turbo hits a preset boost pressure.