Wow, a whole lot of misinformation a here.
Stock PCV system has one intake, passenger side, and one exit, drivers side with the actual PCV valve. Normally manifold vacuum draws the gases out of your crank case via the drivers side. Air flows into the crankcase from the passenger side connected to the intake tube AFTER the MAF so it is METERED air.
Now if you install just a catch can you need it on the drivers side. This set up requires that the system stays attached to the intake tube and manifold.
If you vent to the atmosphere via breathers or a breather/catch can, the flow on the system is reversed. Since you no longer have manifold vacuum pulling it out of the engine it just flows out under pressure from the passenger side. Without the manifold vacuum the PCV valve on the drivers side will not open. So with a system vented to the atmosphere the drivers side does nothing. You don't need to put a catch can on the drivers side if your running any kind of breather.
So, if your running a catch can breather you only need to run the passenger side through the can. You can just cap off everything else.
If you are running a catch can (no breather) it needs to be on the drivers side.
Unless you remove the PCV valve from from the drivers side cam cover, there is no need to run both lines through a catch can.