Alright...
It sounds like you are planning on making this out of metal and that is a horrible idea. Because as we know metal conducts heat really well so as the engine heats up so does the intake pipe defeating the purpose of a "cold" air intake. Custom molded fiberglass would be the suggested way. Doesn't conduct heat like metal and doesn;t melt like PVC.
As to how... you're gonna have to figure that out but i am sure you can pick up a book on he subject somewhere.
DoubleTap