What I meant is that I can easily go to the WIX Filter site and get Micron level Filtration on specific Oil Filters from the spec the give.
For Air Filters the site gives dimensions and Cubic Feet Perminute but no Micron level of filtration.
http://www.wixfilters.com/filterlookup/index.asp

I took a quick look at the site. I did not see any easy way to look up let us say the Filter for my Mercedes.
It also looks like you might have to pay for some of the info.

My Porsche mechanic showed me a 911 intake that had been using a K&N filter to illustrate why NOT to use them. It was loaded with fine dust and grit. The intake on the car next to it with a stock paper filter was perfectly clean.

Pretty grim report for K&N, I always knew I didn't like them, now I know why. I was always too cheap to buy one just to tear it apart and see what makes it "tick". It seems to me if you want to increase volumetric efficiency you would need to start by installing a larger filter, space dosen't always permit. For normal driving conditions why would you want to do any of that. All you need is the ability to safely achieve and maintain the legal speed limit, economy comes from the weight of the foot on the accelerator pedal, assuming the engine is properly tuned.

K&N Air Filter
 

I have a 1998 E320 with 111k miles on it. I've just replaced all 12 spark plugs and the original Mercedes air filter to K&N air filter. I do notice the difference when using the original Mercedes air filter, the engine seems like wanting more air, but not able to. With K&N, it seems more air flow to the engine. I do pray that it will not bust my air sensor.

I hope you are not pulling my leg, because I am been told with different stories about how good the K&N air filter performs. I have placed back the original and thanks for the link.

K&N Filters
 

The K&N filter probably do improve performance a tad. This performance would come while you destroy your engine in my opinion. The K&N filters do not remove anywhere near what a good Brand of filter does. This is especially true when they are not maintained properly.