I'm not sure we're all talking about the same ducting here...... and
apparently the syncho question involves a different area of the engine bay.

As for the Vanagon... are you sure it's supposed to fit up right into the
vent hole?  I've still got my original tube, and it appears to only be long
enough for resting NEAR the vent.  Also what if you just remove it, and run
without the vent.  Wouldn't there be enough air coming in from the
remaining part of the tube as it is?

Regards,
Shawn.