I just put one of these on my Forester. There's a couple hoses from the valve covers and the PCV that go into the intake manifold that have blow-by gases. Basically the hoses go into the air oil separator and particles and whatnot have the chance to separate from the clean air back into the intake manifold. As engines get older, blow-by gets worse because the pistons don't make such a good seal against the block.Thanks eh!! And what's that for??
I assume that my detonation and my o2 sensor got fouled because of this blow-by crap, so I hope the catch can was a good addition...I have pics of it in my journal if you care to look.