I don't think there's anything inside an after market expansion. OEM ones are double skin, which is why they are heavier

I googled this, but you'll need a lot of technical input http://www.mh-aerotools.de/airfoils/javapipe_en.htm

Things to bear in mind are RC Valves vary the ports and it depends on where you want the power & where you plan to ride. You could end up with great track pipes that are no fun on the road
_________________
Why do things simply when you can complicate them