Aircooled VW South Africa

Hi All,
Besides the obvious single and double intake ports visible on the heads; what is the difference between then w.r.t. kW, torque etc.?
Which works best in a '69 DC ?

Twin port produces more power and torque right across the rev range. I've posted the graphs here before; I'll see if I can find them again.

Single port 1600:


Twin port 1600


Be careful when comparing the above graphs, the torque scales differ.