BCA, Boost control actuator... diaphram thingy, same thing. On mine, the vac line to the top of the BCA goes around to the back side of the black 1" square vacuum manifold on top of the SC inlet. I'm not sure how it would dump at 10 psi, seeing as you don't have the solenoid that makes it dump.

Did you ever unplug the lower chamber of the BCA?

If your BCS isn't wired up to the computer, you're not dumping boost. It's not possible.

Boost
 

I did unplug the lowest vacuum line and fashioned a custom filter.

Why only 10lbs?

Stripped rotor coating from your solvents, high temps, belt slipping, any number of factors.

Go back to the stock pulley (or the one you had on there before) and see what you get. Smaller pulleys don't always get you more power. Sometimes they KILL power. Or gain nothing. There's alot of factors involved here.

With it idling, pull the vacuum line off the top of the BCA. Does the rod extend all the way so the foot on the end rests against the base of the SC?