INTAKE MANIFOLD DESIGN: How The Big Boys Do It
 

This guy compiled a short history on the Audi intake manifold. Good info here.

http://www.bufkinengineering.com/intake%20manifolds.htm

The Twin Plenum design makes good sense over a log in that it allows air to inter equally to all the cylinders.
I found more info on this site.

http://www.vwdiesel.net/forum/index.php?topic=27504.0

Also if you Google Twin Plenum Intake Design you will find some more interesting ideas.
Cheers,
-JB

That is a very good find. Cheers.