Yes, more air flow = more HP. That's not disputed.

But larger air flow doesn't have to mean poorer filtration. One way is to use the same paper filter as OEM, but make the area 10x bigger. Not real convenient 'cause there's only so much room in the airfilter housing. But then you don't let more dirt through.

That doesn't say K&N is better or worse, because it's a bit different anyway. Comparing pore size is only valid if both filters are NOT oiled, or if both are oiled with the same oil. When the pore size and the tortuosity is the same, an oiled filter will remove more particulates simply because they stick to the oil.

There's also the idea that particulates below a certain size aren't really harmful to your engine anyway. They're carried through and don't drop out to the walls where they would promote abrasion.

 

No fear is what it is...

 

I did a lot of research about cabin filters and what features to look for. The 5 layer carbon filter is best, and the only company I found that offers this is Bosch. For some cars, only their 3 layer filter is available. This still has up to 100% particle filtering and is electrostatically charged, which is much better than the competitors' (FRAM fresh breeze, Purolator) product. Oil can Henry has their product which is similar to Bosch's, but it will cost you much more.