grandmaster

Did you find a fix for this yet? We just bought a 2005 gx470 with the exact same problem and it does seem to be worse when it is colder outside.

K&N let quite a bit of fine dust in. Take your K&N filter out... take a white paper towel and wipe the inside of the air intake (behind the filter where it should be only clean air) and you will be impressed with the amount of dust it lets through. Great for airflow but i'm very leary about how much ultra fine dust it captures.. considering you visibly see holes in the cotton.