Here is Jim Akiba's suggested Colluder Cone. This mod was created by
my friend Bob Parsons (rest in peace) and posted in the photo section
of the Subaru Vanagon List. Bob claimed significantly improved MPG as
a result.

http://autos.ph.groups.yahoo.com/group/subaruvanagon/photos/browse/912a

Beautiful isn't it?

Gracias,
 Miguel