[lippy]

I meant that port area is fixed over time, not at different elevations in the port. If two ports flow the same and one has a smaller cross section, then velocity will be higher across that port, like in a venturi. It seems to me that flow and velocity need to be proportional.

But I think i get what you are explaining. Similar to an intake runner, the "natural frequency" of the flow can be optimized for a particular operating range. So some ports that flow well won't work well on a specific engine.