Yah, that's kind of a ram air effect. Air inside the runners would be accelerated toward the cylinder by the action of the intake stroke, and when the intake valve closes, the moving air would then stop against the closed valve. This would raise pressure right at the intake valve, and would lower pumping losses as the intake valve opens again. Longer runners allow the air to achieve a higher velocity than shorter runners.
Gee, so ram air turns out to be good for ecomodding after all... But only if the ram air is past the throttle!
