Once had to cover the air cleaners on a BJ8 to drive through some ash from Mt. St. Hellens. Wish I had K&N filter instead.
Lots of misunderstanding out there about filters and air horns or velocity stacks.
Read what David Visard has written. He has shown that a properly sized K&N fitted with a properly designed "stub-stack" inside will outperform anything else.
C Ya,
Mark