The one to the right usually attaches to the ford standard breather system which has a one way valve to pressurise it, (I think). You can run either side to the ECU or boost gauge as both see the same system pressure.

The reason you have to block the metering head up is the standard system uses the metering head to mainly dump oil into the inlet for some reason, usually a sign of some issues internally.

When you fit the after market system you have to block the hole as it created an air leak in the system. All of my 1.6 turbo's have had this hole blocked up as it makes the engine breath better and reduces crank case pressure. It also spits the oil either back into the sump or, as I had it, a pipe over the gearbox which meant you didn't get it back in the inlet.

All should work fine as is.

One things if you have high crankcase pressure it is usually a sign of piston ring wear and combustion pressure being passed into the sump. This is a sign the bottom end will need some TLC.

If you have any other issues drop me a pm.

I hope it helps.