Boostvalve doesn't bleed anywhere. It has a check ball that keeps the boost in the manifold till the pre set pressure, at which point, it release it and the pressure activates the wastegate.

I see. In fact I think that's what I have somewhere in the garage. It should have a vent, not to be mistaken with a bleed port, so the wastegate isn't stuck open until the setpoint is reached again, right?

Sixto
87 300D

http://www.boostvalve.com/faq.html

It has no vent that I have seen. Pressure in the manifold is prevented from going to open the wastegate until it gets to the right pressure then it pushes the ball open and pushes the wastegate open.

Say the ball is set to pop at 10psi. Boost gets above 10psi and the ball pops to allow boost to the wastegate. The wastegate opens and boost drops. As boost drops to, say, 9psi, the ball closes. The wastegate is still partially open because there's 9psi downstream of the ball, right? I think you need the tiniest vent downstream of the ball and account for the bleed effect when setting spring tension. The setscrew threads could well be the vent.

Sixto
87 300D

I would imagine that the spring would not allow the gate to stay open plus there is pressure in the turbo