to get the correct reading your thinking of....you must put in new plugs....drive the hell out of the car...then right after you floored it shut off the car and check the plugs. do not let it idle since that could case the fuel to burn off the plugs. cars dont run rich on idle....or at least most dont. that is the only true way of telling of the mixture. you cn get close by taking ut the plugs at 7,000 but did your car idle for long periods of time?