Not to set this thread adrift, but SS mentioned a point I've seen posted more tha once and more than one place - that K & Ns pass more particulate matter than paper filters.
I have not seen definitive proof either way. I ran K & N on the Ducatis, and have one on the R 80 ST.
To hedge my bets on the ST, I bought a sheet of Uni Filter foam and cut out a prefilter that fits across the top of the K & N. I can sleep well knowing that I have top notch filtering. AND, the prefilter and filter are cleanable and reusable. The Uni Foam didn't even force the need for idle mix nor needle adjustment.
Works for me.
Merritt Island, FL
When a person asks you for advice, they don't want advice. They want corroboration.