Freeing up the air
From what I read that seems to be true. Systems like "Max Air" and such that make truly large changes in air intake are necessary to make a significant change. Along with this comes an increase in "top end noise" as well. From what I hear to get much increase at all you need to go the whole route. Intake, jets, and exhaust. Changing air flow through the whole engine and then increasing fuel, to restore fuel air mixture.
Dave