360 vacuum leak.

A working PCV valve should be closed at idle because the valve is sucked closed by high vacuum. It sounds to me that you have a valve that is stuck open, causing a significant vacuum leak at idle. A properly working valve should have no effect on the idle mixture.

That said, fixing your breather setup is a must, because a pcv valve on the same side as a breather does nothing at all. The breather is preventing the pcv from pulling air through the crankcase.