[MENTION=13630]DRIFTER[/MENTION] is right- the best air filter for the NSX is the OEM paper element. Period. No matter how careful you are, all of the oiled filters will, over time, deposit that oil into your throttle body and intake manifold, where it will gum up the small vacuum ports that are critical to the proper operation of your engine. Any claimed power gains are within the error margin for a dyno. The OEM air box is good up to about 350 hp with minimal restriction. This has been extensively tested in Japan.