I have an inline four in my van, but it uses the regular Vanagon air
filter.  To get clean and cool  intake air, I ran a brake duct hose up into
the right hand corner engine  bay vent hole.  You can get flexible brake
duct from auto supply houses or race supply sites.  I simply ran a bit of
wire down into the louvers  from the outside till it emerged into the engine
bay.  Then I attached that wire to a length of brake duct hose that was
clamped onto the airbox inlet.  Pull the hose back up into the corner of the
body  with the wire and neatly attach it up inside...cut off the excess wire
and you have a 'fresh air snorkel' up away from engine heat and most of the
dust.  Using the same diameter hose as the inlet into the air filter doesn't
reduce the volume of air.  Getting it from the outside, it's much cooler
than taking air out of the enclosed engine compartment..

  Cool fresh intake air was worth (dyno confirmed) almost 10 additional hp
on my other car..about 4% improvement in power..

  Don Hanson