Somehow I would think that the unported Speedmaster would be equal or a little better flow over very lightly home ported 596 heads?
Also when I was referring to this mile per hour gain I was really referring to the CNC heads.
Spend 60 bucks and have 'in your opinion' the best port of your 596 flow tested.
That's how you make your decision.
Any other way is like doing it blind folded..
of which many big name builders love selling **** to guys like you.