I've already made my comments about K&N filters on a previous thread, but would like to add someting additional. Skip Barber Racing School gets all their cars and engines from Dodge. These cars are returned to Dodge at the end of each racing season for resale as 'program cars' They all use K&N air filters. Jim Russell Racing School fields Mitsubishi and Mazda rotary engined cars. They too use K&N air filters. I can't believe that the Skip Barber or Jim Russell schools would use a product that would harm their engines; least of all would Dodge let them do so! Ask almost any amateur (and many pro) racecar engine builder which is the best air cleaner, and 99% of the time you'll hear "K&N", or one of the newer K&N wannabee's. They spend many thousands of dollars on their engines and, for the most part, also wouldn't use something that could potentially cause damage. Let's not forget that it wasn't too many years ago, before replaceable paper filters, that almost every car had an oil bath filtering system. Why? Because it worked! You would probably see them in use today if it weren't for 1) no room under the hood, 2) costs the auto maker more initially, 3) requires regular maintenance. Let's face it - some folks just won't spend the time or energy to clean and lubricate a K&N filter, but those are the same ones that will 'run' a paper filter for years on end and then wonder why their engine performance isn't what it used to be.
Lastly, I've heard about comparison charts several times now, but would very much like to see them for myself. Is it possible for someone to provide a link to them?