joel95ex: One thing to bear in mind are the operating conditions. If you ran the car in a relatively clean environment, dirt wouldn't be much of an issue. I had an oiled cotton gauze filter (not a K&N) and got really spooked with one of my trail 4x4s when, at the beginning of all this debate nearly 10 years ago, I ran a smear of grease in the filter housing on the clean side. After 5-6K, it had collected a large amount of grit. I was operating that truck in an incredibly dusty and dirty environment. I think that problem could have been cured that by installing one of those foam pre-filters but they weren't available for my filter size at the time. I ended up converting to a huge, remote air filter from a big farm tractor. Conversely, I had a K&N replacement element on a city driven 4x2 pickup for years and the grease smear trick yielded no grit and the truck lived a long, happy life.
The UOA is the telling tale. It's clear, and you proved it, that engines can have a threshold tolerance for such material. I prefer not to test my engine's tolerance in that way, however.
I disagree with Doubledee's blanket statement that the performance gain of a K&N, or any cotton gauze filter, is zero. It all depends on the flow rating of what was replaced vs what it was replaced with. In the old days, K&N's heyday, many cars used undersized filters or restrictive housings and the K&N could offer a benefit in that situation, even at stock power/airflow levels. Today that is much less true and virtually any performance replacement element is hard pressed to offer any gain on a stock engine. If you increase the engine's airflow requirements with other mods, you might be outstripping the stock element or housing's ability to flow enough air, so a higher flow element or system is necessary. Or more necessary. In that case, it's not so much GAINING power, it's not LOSING it due to intake restriction. You can tune in some power on a stock engine with the right ducting, but again, it's often minimal and usually only at the upper end.
The thing that attracts me back to performance filter elements is the cleanability aspects. I am pretty happy with the AEM I've been running lately. They filter well, though are a bit more restrictive than the cotton gauze types. Plus... no oil!! The best part is that AEM had SWRI runs some pretty severe tests on their filters, repeatedly abusing them during cleaning, and the filtering ability stayed copacetic. They have all the test results on their site.
