The harshest restriction is the air filter, plus any significant right angle bends and other restrictions in the system. Unless you change the pipework going into the filter and the pipework going from the filter to the turbo, all you are achieving is exactly what my analogy stated. And using a Donaldson air filter for the flow bench testing does not test the system in real world applications. The flow improvement with the Donaldson is approx 15% (only at the filter assembly), will it be this much with a Nissan filter?
As part of a completely modified system, this component may work very well. On it's own, with no modifications to the air intake system, I simply can't see that it will provide substantial performance improvements. I'm not saying that it cannot work, but on its own, I see it as pretty limiting.
Cheers
Ray