i had the big 60k service including the cambelt in december, also replaced standard plugs with denso ik20s. my fuel consumption also has dropped to 250 miles to the tank, after doing a few searches i ve noted a lot of you have reset the ecu. so i re seted the ecu and so far i have done 200 miles on half a tank, so im hoping to acheieve 400 miles by the time the light comes on. i would try this first, also check air filter housing and sensor is seated correctly.