It goes right back to your original post of increasing capacity or efficiency...flowing more air in and out not only effects efficiency, but also has a big effect on dynamic dispacement. the static capacity of you motor is measured at rest and is a fixed value, but during operation numerous factors change that volume such as ignition and valve timing, valve angle, and size, as well as intake variables and exhaust...not just the removal of restrictions, but the diameter and leangth of the tubing on both ends effect the flow and wave pulses dramatically. This all effects how much air is actually in the chamber at combustion...and power output. Small changes in the length and diamer to of the intake tube alone can significantly move the power band up or down, etc...

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Atlas Gray Cayman S