I am not a K&N pusher, but use the product. There are a lot of people on here who dislike them. So here is the place to discuss.
From the K&N site,
http://www.knfilters.com/testmethod.htm
http://www.knfilters.com/efficiency_testing.htm
Other opinions
http://www.duramax-diesel.com/spicer/index.htm
My experience,
1999 Camaro - 90,000 miles, no issues K&N on since new.
2003 ZO6 Magnacharged - No issue's with K&N kit 15,000 miles (sold)
2002 Jeep Rubicon - No issue's 50,000 miles K&N and Gibson Exhaust Nice power gains with the two (Sold)
2004 Infinity FX35 - No issues K&N 75,000 miles (Sold)
2005 Big Dog Chopper - No issue's, K&N added per dealer request, and no I did not purchase it from them.
