My mom has a 2003 Monte Carlo SS. Every 3 to 5 months her car rough idles and the check engine light comes on. She has been told by the chevy dealer that the issue is related to the intake valve. She has had it cleaned several times as well as having had it replaced once. It hasn't fixed the issue. Also, she needs a quart of oil every 1000 miles. It never leaks out of the car and no one can tell where it goes. GM is paying for the oil as she bought the car new and has had this issue since 2003. Can anyone please help?