Al, on the PCV - Breather. This is how I understand and envision it. The PCV system Positive Crankcase Ventilation, is set up to relieve pressure in the crank case as you said. It replaced the old road draft tubes that use to just vent into the atmosphere. The idea was to pull any blow by into the motor to be burned in the normal combustion process, but I am sure you know that.

The system creates a suction at one point in the crank case, usually a valve cover, but I have seen them in valley covers and other locations too. This connection is sucking air out of the crank case, in order for it to work effectively you need to let air into the crank case some place else, usually in an opposite valve cover to create a cross flow of air through the crank case. The breather is designed to let air into the motor, not vent it out. If you look at most stock air cleaners, they have either a metal tube or a hose that goes to a valve cover. Inside the air cleaner is a small filter right where that tube connects. That filter is to clean the air being pulled into the crank case. On aftermarket air filtration systems the need still exists to let air into the crank case so people put a breather on the opposite side from the PCV connection. I hope I have explained this correctly, if not please refer to my signature line

Pat