What are you using for a boost controller? As you have a Link G4 you just need a Mac solenoid valve and the G4 can do sophisticated boost control.
Have you checked the vacuum line to the bov?
Is there someone nearby you could swap with for a test?
If you decide the bov is faulty I have a pair of GTR bovs which are much more robust than the RB25 ones and bolt straight up in the same place (although you need to adapt the outlet pipe as the GTR one is bigger).
I am after $100 for the pair posted but could do you one for $60 posted.