Well, basically, your 8psi actuator spring will hold the wastegate shut until the turbine housing pressure reaches or exceeds 8psi (Theoretical, as its different due to teh size of the wastagate penny).

However, with its the actuators signal connection blocked and airtight or with its slight calibrated bleed, 8psi pressure is not enough to operate the 8psi spring due to the depression that is created behind it within teh capsule and thus in essence, the spring rating is increased which is of course why you can run far more boost with air injectors in the first place.

Does that make sense?