And we all know this is true because K&N tells us so... If you need to pass even more air than a clean stock filter, then the cheapest and easiest thing to do would be to toss the filter in the trash and run nothing at all. Of course, you wouldn't think of doing that. You want clean air going into your motor. That's why there's a filter in the first place. If a K&N filter is the same size as a stock filter and it passes more air, then it passes more dirt, too. You just have to decide whether you want clean air or more air...