Pulled this from another site..
wow. there are a lot of people with misconceptions about the pvc system.
the port on the valve cover is to allow fresh air to go into the engine. it's on the front side of the throttle plate. there is no vacuum there, ever. the pvc valve is connected to the intake manifold behind the throttle plate. as long as the throttle is closed, i.e. idle, the pvc has vacuum on it and is sucked open. it draws air through the engine from the vc port. the idea is to suck the oil vapors out of the engine.
even during cruising there is some vacuum on the intake manifold making the pvc system work. boosted engines can still benefit from pvc system. as for the vc having vapors sucked out of it, that's not possible. when the engine is pressurized from blow by, that will push vapors out of the valve cover port into the intake tube. if you put a vacuum gauge on the intake tube going to the vc, you will never see vacuum on it.
This has always been a big debate on KA-T.org. The SR PCV system is much more ideal for turbo, for obvious reasons. For the turbo KA the general consensus is to replace the PCV valve with a 3/8x3/8 fitting (which is precisely the same part as the PCV valve, minus the valve part), run a hose from fitting to catch can, and from catch can to pre turbo intake pipe. As for the valve cover, VTA. Thats about the best you can do short of redesigning it on your own.
Remove PCV valve. Install 3/8ths NPT fitting in place. Run hose to ground or vented can.
Valve cover fitting. Turn it counter clockwise and run 5/8ths hose to back of engine bay and down towards tranny case...Or to a vented can.
Plug Throttle body boot fitting with 5/8ths Cap.
And obviously cap the the Vacuum tree that the PCV was connected to.