[Longhorn Man]

to simplify an explination...

You have the kitchen that is filled with smoke. you have 2 windows in the kitchen.
1 open both windows
2 open both windiws, and put a window fan in one of them blowing the smoke out.

The PCV does the job of the fan.

When you only have vents, or the old style road draft tube, the oil gets contaminated with acids that form as a natural byproduct of the combustion. The PCV sucks it out, along with trapped humidity, and the aformentioned blow by.
On the other valve cover, you need a breather to let clean air in. The easy way, is just a chrome Mr Gasket breather. The better way would be a 3/8 hose going to the air filter to pick up air that has already been filtered, and is clean.