Obviously, this relates to Toyota directly and not necessarily other manufacturers, but I saw this last week and thought it was interesting. A study conducted by a Toyota Parts dealer in Kansas--Toyota OEM, K&N, and Wix came out on top. They did a comparison of Tacoma/Tundra filters: http://partsblog.olathetoyota.com/1654/oil-filter-comparison-best-filters/. The results are posted to an external site noted in the article. They admit they didn't do a filter medium performance test, but they did a comparison of design/microscopic filter observations/etc.
The Tacoma study related to the Camry as well: http://partsblog.olathetoyota.com/4980/toyota-camry-oil-filter-best/
Also relates to this thread: http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3486260/2
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