K+N Breather filters...what do they do?

[Karl Shultz <karl.shultz@ibm.net>]

All,

At a recent autocross, I looked under the hood of a very fast B. 
Instead of the breather hoses running to the charcoal canister, there
was a little K and N filter attached.  I've seen these things before.

What do they do?  I might like to try them on either car.

-- 
Karl Shultz
95 Integra GS-R, black, loud, low
73 MGB, orange, sputtering badly