At what pressure does it vent? The intake pressure might
not get high enough to trigger it.

I believe the bypass valving is integral with the turbo so it
probably can't be easily defeated.

Also, aren't you venting metered air with a blow-off valve?
I would think that would confuse the ECU since once air is past
the air filter it is metered and it is assumed it will pass
through the engine. I know others have done this and I don't
recall them mentioning any problems with this, though (just
wondering if you reserached that aspect).