What the poster before and after myself and probably many others is how these heads flow. Most places show there results of there flow bench testing of the head there selling.
I've seen heads that had a legit 30 CFM more than the exact same head and make less power. Seen that many times. There is no way to quantify things like turbulence, localized reverse flow and many other things. So really, looking at flow numbers only is just for marketing.