no one has ever had all the tuners best flowing cvh heads and tried them on the same car on the same day to see which one produced the most power so this would be a question that no one would know the answer to.
going from a standard mfi head to a ported head you would see a huge improvement and then that head would be recommended to all, and because a car does the numbers does'nt mean the cylinder head the best there are so many other factors to take into account. But you wont go wrong acquiring a head from nms,area six,pumaracing,cnc heads,jamsport and a few others i have'nt mentioned they all achieve vast improvements over standard...
sean