Chuck,
I don't think it makes much difference what air filtration system Bill
uses.
Wherever he's taking is van, the paper filter has got to be plugged
solid, and the K&N, won't stop anything that he's driving in.
His neighborhood must be in the Gobi Desert.
Nice point about the foam pre- filter.
If one was to venture out in a very dusty conditions, all the time the
foam pre- filer is absolutely necessary, regardless what air filter your
using.

Later,

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Terry 85 GL