The 701 (Enduro) air box is designed to promote air velocity. This promotes low end and mid-range. (And let's face it, the 701 NEEDS all the help it can get in this regard, in stock form.) It hits it's max about 5600 RPM. Fueling takes over from there, to give it a top end rush. Tuning only slightly enhances the top-end, but REALLY makes the bottom/mid-range come alive. This reduces the "surge" felt from the lazy bottom/mid to the bristling top-end. But, it is still hauling butt. Even more-so.
Awe Hell, nevermind. I'm getting into aerodynamics and flow characteristics now.
How about this....Always use an air filter on anything you care about.