Only complicated and expensive multi-axis CNC programs can imitate the complex shapes the cylinder head porter develops as necessary for optimum flow . This why hand porting is , and will continue to be , in small runs, the only and BEST alternative to that technique. Understanding different design philosophies is key to achieving maximum results. Needless to say, comparing maximum CFM flow at full valve lift is somewhat misleading at best, and less than professional at worst. This knowledge has been hard won over the years and is one remaining area of secrecy.
Small mistakes can cost a lot of power.