I just got rid of the K&N's on my vehicles....I wiped the throttle bodies over time and yes they were clean, but then i thought, why would dust be sticking to it? If everything is dry, then dust wouldn't stick to it----forward to this morning, I got my AEM dryflow and wiped the intake tube near the filter end----DIRTY---well the K&N oil barely visible after the red dye went away was providing adhesive for all the fine dust that the filter was letting in... the rest was sucked into the engine. my recommendation: get rid of the K&N....if you really believe there is a mileage drop, just think of the money you'll save by keeping a "paid-off" vehicle running for a while..