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I think a normal PVC valve will seal under pressure - like from backfire, so it will probably be fine with some amount of boost and not pressurize the engine.

Even if the PVC lets boost pressure into the block, unless it badly overwhelms the breather I don't see there being enough pressure to blow out a seal or gasket, but if it allowed the supercharger to pump an air fuel mix into the block and that popped anything is possible.