I would doubt their own theory *dirtier they get the better filtration* as that just goes against all air filter common sense. Besides that - you probably won't see them advertise a dirty filter will give you the same airflow as a clean one, which....defeats their claims on both ends.
K&N's are for horsepower & more airflow (theoretically) and probably not a good idea for dusty conditions anyway.
I never saw dust past my filter when I cleaned it every 6 months. The dustier the conditions...the more often it should be cleaned. That's my story anyway, and I'm sticking to it.
Everyone else can make their own decisions based on the positive and/or the negative feedback.
"The dirt particles collected on the surface of a K&N element have little effect on air flow during much of its service life because there are no small holes to clog. Particles are stopped by layers of crisscrossed cotton fibers and held in suspension by the oil. As the filter begins to collect debris, an additional form of filter action begins to take place because air must first pass through the dirt particles trapped on the surface. That means a K&N air filter continues to exhibit high air flow throughout the life of the filter while it is accumulating dirt. So as dirt accumulates, the performance advantages of a K&N air filter can increase!"
Exactly....K&N claims their filters have tested no lower then 96% so it means 4% of the crud makes it past (worst case). No more for me, but I have a used one if anyone wants to buy it.
More fuel for the fire!
I put the TRD CAI on my Tacoma almost as soon as I bought it new. 85K miles on it now. Just yesterday I did a little preventative maintenance, cleaned the filter, pulled mass air flow sensor, pulled the tube to the throttle body. Did the white glove test, actually white paper towel, on the front of the throttle body clean as a whistle, mass air flow sensor (never been cleaned) bright and shiny.
I have a K&N in my '86 500 Interceptor, been there since around 18K miles, now at 45K still is with in factory compression specs, no problems related to intake air dirt, air box is always clean, changed out carbs for the larger '84-85 versions at 42K, old carbs and intake boots clean inside. This on an engine that is very fragile compared to the GR1-FE and runs about close to a 1000 rpms per 10 miles an hour in 6th with factory final drive gearing.
160K on my '92 Ranger 4.0 K&N no engine problems related to dirt getting past the filter. 8 paper air filters in that mileage = reasonable=at least $80. $40 something for the K&N=I'm ahead if I don't look at my labor to clean and the minimal amount of oil.
Sorry your results varied.
Your price does not include the filter cleaner and oil so tack on another $25.00 to your costs.
Also I can swap my filter out in 5 minutes on the trail if it gets damaged or full of moisture or full of dust. You must wait hours for yours to dry after cleaning before you can even oil it and that can not be done on the trail unless you carry a kitchen sink with you