I'm sure there has been an attempt at a formula of some sorts. I've never encountered one. To my simplistic way of thinking, it's as much an art as a science. The VE of any given engine will determine the volumetric needs, and that is affected by chamber design, valve position and design, valve timing, RPM, and various other factors including the intake design. Presuming a "perfect" intake, one might extract a given runner area (cross sectional) for a given pressure drop. Unfortunately, there are dynamic forces within the intake runners themselves which affect the overall flow. That was one of the original intents of the CFI (and TPI, and most other intakes).
As a result, both conventional fluid flow dynamics and sonic wave/pressure theories are involved. How they will overlap with any particular combination is your question. Search for theories about the "Mesh Method" as described by Roland Benson. His texts may have some helpful information.
One crude, incomplete formula is as follows: Peak torque rpm = (cross section area x 88200)/cylinder volume.
Last edited by Vader; 12-27-2005 at 02:54 PM.