I'm not the best at expaining things sometimes, but here are a few links:
look like half way down.
If you look at the picture at the bottom of the porsche page, you can see pulses generated by the intake valve closing. these pulses vary with rpm. But you can harness thier power by having a place in the intake runner for them to bounce back off and charge the air going into the cylinder. There is a valve that ususally opens to give the charge a place to bounce off. The placement of this point and the rpm at which the valve opens is critical to make this actually work.
Here are some super simple pics i did in paint:
The blue is the air and the red is a pulse conducted by the air, not the air moving back up.
Here is the air traveling it'* normal path:
Here is the air being charged by the pulses generated by the closing valve
Hope that helps ya out,
Nissan has two variations of this that i know about that are on maximas overseas.