I've been suffering from the dreaded late 2nd turbo syndrome, where the EGBV doesn't open. Just spent ages checking all the hoses, testing the VSV, blowing down hoses and checking everything. Nothing wrong. Then I realised what I'd done.
I recently fiddled with my Emanage map. I run higher than stock fuel pressure, with fueling trimmed down where not needed. On the Emanage this is done by scaling the MAP signal down in a table with RPM on one axis and throttle position on the other. That's a base if you like, to which you add fuel in an injector table which has RPM on one axis and boost on the other.
Unfortunately I scaled down the MAP signal so much that the ECU is deciding it doesn't need to open the EGBV. Doh! Time to rejig my map I think. Anyway, thought I'd share that duh! moment in case anyone else tries something similar!