Just because the boost doesn't go over 10psi with the wastegate disconnected, doesn't necessarily mean the wastegate isn't working properly, or that it is partially stuck. Simple test: Use a Mity-Vac to apply pressure to the wastegate. You should be able to visibly see the actuator rod move as pressure increases, and it should move smoothly. I've done this on my 603 (with a Garrett turbo).