It's pretty simple (ha ha). Basically, your intake pipe is a closed resonator - that is, it has a resonant frequency which depents on length. You tune the length to a specific engine RPM so that subsequent air "pulses" are arriving at the valves right when they open. If you really wanted a tuned CAI, buy an AEM V2. It's tuned to 2 frequencies using 2 diameter pipes in order to maximize power in the lower RPM range as well as the upper.