I used to run a conventional PCV system This type of system does nothing to create vac in the crankcase. I have a MAP sensor on the crankcase and I was getting positive pressure in the crankcase with a conventional PCV system. And I was always getting oil leaks. No mater how many times I sealed it up, it would always leak oil. I had to keep mats under it to sock up all the oil.
So, this is what I did to fix the problem. I got a fixed orifice PCV valve. I then put a one way check valve in the line between the PCV and the manifold so it could only pull vac in the direction of the manifold. I then put a restriction in the vent line going from the breather in the other valve cover to the TB. I then played with the sizes of the PVC valve and the restriction in the vent line until I got about 7" of vac in the crankcase. Then I T'ed off the vent line and connected an electric smog pump. And then I put an one way check valve before the pump. As I am driving around the crankcase gets it's vac from manifold vac and when the vac in the crankcase drops below 3.5" of vac or I go to WOT the ECU turns the smog pump turns on and it keeps the crankcase vac at around 5" of vac. Since doing this all my oil leaks have stopped and the mats are now gone. And as a bonus the vac in the crankcase helps ring seal.