my '99 gt has started dying at idle. i used a k&n filter from the time i had the car until about 8000 miles ago when i changed to a k&n fipk. i cleaned the sensor. it idles fine when the diagnostic setting is run from the computer. it just won't idle at a stoplight. it is not running rich or lean and i get great mileage and performance. everything seems fine except the idle. anyone else out there seen this problem?