K&N says their filters demonstrate a cumulative filtration efficiency of between 96% and 99%.
They don't compare their numbers to OEM stock filters so it's somewhat of a meaningless specification.
I still run a stock air filter out of fear of ingesting sand and dirt into my engine. The charts show a gain in power/torque but do they really filter as good as they say they do? I would like to let my engine breath better but not at the cost of loosing compression over time.
If those filter systems were that good, I would think some of the specialty cars would come DIRECTLY from the factory with them. An example would be the Shelby Mustang GT 500. Not one produces the claimed 500HP in FACTORY trim & could use all the extra help they can get to meet spec. But I think the factory won't use them because of the dirt they allow to pass.(?)
I know the factory system does trap the dirt well.
Just wondering what others think about possible engine wear verses the small gain in performance.