I got to watch what I say from now on.
http://www.sa-motorsports.com/diyport.shtm
Lots of good info here. Its all about flow in the valve area. tight turns and edges make drag that slows down the air travel.
This will be my next buy I hope.
Rapido 2.3L Turbo Aluminum Cylinder Head
http://rapidogroup.com/newprod.htm#cylinderhead