I have seen good results from both the old paper type elements and K&N.
The most sucessful results from the K&N were on a Super Late Model. The car owner kept about four or five filters cleaned, oiled, and ready. He would run a clean filter and an outerwear every time the car went on the track. It didn't matter if he was packing the track, hot lapping, heat race or feature race, he would change the filter and outerwear. His air filter also had a sure seal on the bottom and rubber seal on top.
The sure seal is an oringed adapter, hence the name sure seal.
The rubber washer seals the top.
The outer wear is a cover that helps prefilter the air.
I don't understand how a K&N filter could possibly get these kind of results. When you hold one up to the light you can see what looks like pin holes that should help flow but let dirt thru. You apply oil to it, this should help it trap dirt, but it should also create a flow restriction.
I think he always ran a 14"x6" for a 355cu in motor and claimed it to be a minum for this size motor. I have no idea how often he replaced his stock of filters. I think his filter budget and maintanence schedual might scare most people, myself included.
I also had a customer with an SCCA A/Sedan Mustang that ran a K&N and he made better power than most and won the Runoffs in Mid Ohio a couple of years back. A lot cleaner enviroment and spec 302. Not as much air flow requirements.
Both of these customers claimed better performance, but both were constantly hunting improvements and subject to make several changes everytime they went to the track rather than one at a time. On a dirt car you can't hardly rely on lap times because the track changes as you race.
I have seen good results from plain paper type filters. When I worked for Lone Star Racing we sold lots of Moroso filters and they did a great job. I had a little spare time one day so I sifted thru the boxes and found one that they didn't properly shave the name off of. Atlas filters in Moroso boxes. Not a special filter just a good old Atlas filter.
At the plant where I work I have two 75 hp, two 150 hp, and two 200 hp Ingersol Rand compressors. These are screw type compressors like the Eaton SC and they do not like contaminants. They have paper type elements. As a side note they now offer a prefilter. It looks alot like an Outer Wear to me. Maybe the best of both setups combined?
This is where I wil confess to making a narrow minded decision based on preconcieved ideas, laziness, and habit. I would rather run a paper filter and change it when it looks dirty. Cheap quick and easy, plus it does a great job. If I had to pick one on looks it would be a K&N they just look cool. I like the way they look and I can't dispute how well they function when properly serviced but I will take the paper route.
It would be nice to get some realtime track results from the dragstrip. Now that I think of it I don't know anyone who has made their decesion dased only on hard facts. I don't give much thought to a companies claimed results. This is another opinion, influenced by false claims.