Lately gas mileage way off. Car just went thru inspection and barely passed on HC. Reading of 205 ppm against limits of 220ppm. Recent Audi plugs (6000 miles approx) and O2 sensor( 10,000 approx). K & N about 3000 miles ago. Noticed small INCREASE in mileage after new filter installed. Everything looks O.K. Car runs good. Am I missing something obvious? TIA Regards, Jerry 91 200 STEADIA3qw