Don't have the A to B, but consider this: Any restrictions in either intake or exhaust disturb the flow of air and create bumps/ swirls/ turbulence in the flow. Now, increase the intensity with forced induction. Those disturbances become mountains of restriction ( watch the water flow in a river around a rock or stump. The faster the water is moving, the bigger the effect). Porting is even more critical the more air you flow.