Originally Posted by gomer_110

I believe the difference is in the runner length/size. This is why people typically claim a slight loss at the top end but gains in the mid-range. The difference between the two is not something you can simply modify the Z34 manifold to get.

What I would love to see is variable intake runner tech in a manifold. I think some sport bikes currently have this tech. Basically the runners lengthen at low rpms to increase torque and then shorten as rpms increase to get better top end. Maybe someday.