Right, out of K&N, Green Cotton, Jetex, Pipercross, Powertec, ITG, the powertec filter was found to be the least restrictive, but its a metal gauze design that is known not to catch small particles. The next best was the Jetex, which was a cotton filter.
That would get my vote, as cotton is renowned to be the best at filtering out of foam, cotton and metal gauze. Faiing that, green cotton was next best.
K&N was found to be the most restrictive out of all of them.
Hope this helps