A PCV valve is not designed to work in a closed system so it will open completely as soon as crankcase vacuum over comes manifold vacuum minus the PCV valve spring pressure. The only restriction is up until that point right after the engine is started or there is enough blowby (or leak) from the rings to close it again.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)