Pretend your lips are the intake manifold. If you suck the valve will allow airflow, if your blow, it will close.
You only need a single in/out on the can. The left, right and centre of the engine crankcase are all connected. There are plenty of routing diagrams on this site. I installed the Mike Norris can recently, it's a very nice piece.
2001 WS6 - 6 speed