I haven’t got an EJ25(or any Subaru) but I have vented my PCV to atmosphere... I feel the main benefit is that there is less oil gunk in the TB...
However, the lack of oil vapors in the intake charge could slightly lessen knock (it’s been said that oil in the fuel lessens its octane rating)
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My current Ecotec project...
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My last Ecotec project...
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