You've got me worried now. You say it's not related to engine exploding but didn't find what the problem was.
I'm having the same problem with mine, it doesn't want to make boost but can hit 12psi with the vacuum line pulled off the wastegate actuator.
I'm trying to rule out vacuum leaks and also checked play on the wastegate flap and it is tight against the housing. A friend mentioned the spring in the actuator could be buggered and is opening simply with exhaust pressure.