Ok, but what is a small intake runner (170 cc?) and what is a big one (250cc?)??

What is the influence of the intake manifold in terms of power and torque?
How does a intake manifold influence port velocity and the mixture of the fuel and air?

I read, that World Sportsman II Heads have a similar port volume than that used in factory production heads and that they are good for low speed torque!
What is the intake runner volume, egg. of good old double humps?