Hi,
You make many points, both pro and con, in the argument. The K&N and other gauze-type filters may supply more flow, but at the expense of more grit entering the engine (and consequently the Oil). If that doesn't matter to you (as it doesn't with a Race Engine), then further discussion is moot.
But, consider that in ISO 5011 tests -
http://www.billswebspace.com/AirFilterTest.htm , the gauze-type filters, especially the K&N, repeatedly clogged in ⅓ the time of a conventional paper filter, negating any initial gains pretty quickly.
As you profess an obsession with keeping your filters clean, this wouldn't especially matter. But, for many who don't share this obsession, the gains experienced by a switch are very short-term, and will actually result in a negative sum gain through the service life of the filter. Also, realize and consider that the
longer a filter is in service, the better it actually
filters (but at the expense of increased restriction) as the already trapped particles restrict the size of the pores or openings even further.
But, for many, who are not concerned primarily with flow, nor obsessed by cleaning the filter continuously to insure this, the K&N and other gauze-type filters aren't a good thing. To say nothing of the expense of a shortened Oil Change interval, and potential premature MAF failure. Except for bragging at the Bar, I see little benefit, but lots of negatives.
K&N in particular uses the allure of Marketing and gains out of context to increase their sales. They're not really concerned about the negative effects it can have on you car longterm, nor do they tell the whole story. Similar to what STP did in the '60s and '70s.
If they were so great in a street application, why doesn't a single manufacturer offer them, even as an option where they could mark-up the hell out of the thing?
I
do use a gauze-type filter on my Formula VEE for maximum flow (especially since the filter is only there just to keep
rocks out of the intakes), since regular Oil changes and rebuilds are already part of the deal anyway. But, on my Street Cars, I stick with the OEM paper filters...
Happy Motoring!... Jim'99