I used to run K & N air filters; and my UOA was showing silicon counts in the hundreds, approaching thousands. (Blackstone and other labs caution going over about 20 ppm on silicon).
If you wikipedia silicon; Over 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (about 28% by mass) after oxygen.[7]
http://en.wikipedia.org/wiki/Silicon
Silicon is inescapable; it is in the air we (and our engines) breathe. Silicon is ROCK, and, according to Alan Bender, Director of Oil Analyzers test lab, whom I have spoken to regarding this, the two WORST things in a UOA are iron particles and silicon.
Iron particles are your engine disintegrating (literally and microscopically) and silicon, being harder than iron, will grind and abrade MORE iron into your system. So what's a fellow to do?
I switched to a nanofiber air filter, and my silicon counts dropped to normal levels. I've done this on all three cars I own; and I have UOA on all three.
If you want to Baja race in the desert; run a K&N filter, they are the best air filters in the world for off-road coarse dust. If you drive on pavement, you will encounter FINE dust, and a nanofiber air filter will filter out about 50 times more particulate matter. The US Army uses this technology on the battle proven Abrams tank:
http://www.ultimatesyntheticoil.com/Filters/Ea_Nanofiber_air_filters.htm
And no, I'm not an Amsoil dealer. I would run these filters if Avon or Tupperware sold them. Quality speaks for itself.