Hi All,
If anyone really wants detailed information on different types of air filters
as compared and tested on air flow bench, they should look at Tuning the
"A"series BMC Engine by David Vizard.  Paper has a relatively fast clog rate.
 A K&N filter tested after a 500 mile Baja road race, packed with dust,
flowed 5.1 CFM/sq." as compared to 4.9 CFM/sq." for the average new paper
filter.  A new K&N flowed 6.5 CFM/sq."

This an excellent book of almost 500 pages of no marketing bull as everything
is shown as tested on a dyno or a flow bench.  While it is for the BMC
engine, the principles carry over to all engines.  He has written books
covering other engines but this one is the most thorough.

Cheers,
Kevin Dawson