The bov is just a spacer between the original recurc valve and decent sound
The full replacement as I'm aware replaces the stock valve that is made of plastic with a metal one this is a better option in my opinion if your going to remap intake etc as it will be more durable
I'd say the bov for stock and stage 1
And the replacement for more than that
This is just my opinion as I see it and is open to anyone to add modify whatever
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