When I was in college we did some dirt bike air filter testing with a flow bench, illuminescent powder and many different air filters. The paper and gauze style filters never filtered nearly as well as the foam oil types. That being said, I was very concerned with contamination. I continuously inspected the intake after each and every ride. The filtration of this particular filter element does very well. No contaminants! I am impressed with this mod and eager to get some testing and comparison with our Vericom VC4000 dyno.