Other than the reusability (sp?), I think K&N's are worthless. But then again, it's easier to swap a paper filter than it is to wash the K&N out and oil it again, then wait for it to drain and dry. I don't know about tests on bikes, but on my '98 Z28 it netted NOTHING at the track over a paper filter.
Now, I know that didn't answer what you asked, just thought I'd ad some insight.
If I remember correctly most of the people I've talked to w/K&N 's had no performance gains with the filter. I have a K&N on my bike just because it came with it on there and the only good thing is it is reusable.