OK did some research on how the PCV system works and I guess the drivers side valve cover just needs a breather to pull air from. The breathers usually have little filters on them because the stock one pulls from the air cleaner and is already filtered. The passengers side valve cover has the actual PCV valve and pulls air out to be put back into the intake to be burned.

Do I have that about right? Why have I seen some vehicles that appear to just have breathers on both valve covers and no PCV at all? Also why do some of the breather kits have a shield on them? Which side do you point the shield, towards the engine or away from the engine?

Thanks for any help.