where i lived for 5 yrs, farmland, there was so much dust in the air that you could wash your car, come back an hour later, and the car would be covered in dust that you had to wipe it down with a cloth again. i used a K&N filter for 2 months, after which my check engine light came on for vtec malfunction and the car was idle funny. I pulled off the solenoid and found large grains of sand in the filter screen. opened the intake pipe and found thick dust all over the inside of the pipe. my iac valve was also clogged from the dust and oil. I changed to a weapon-r SW1 foam filter with foam oil, 2 yrs later for fun i opened the intake pipe, there was no detectable amount of dust, my iac valve was spotless, and vtec solenoid screen was completely clear. if thats not proof idk what is. same driving conditions too.