I have a 98 Olds intrigue with only 68K miles. Recently when idling the car will shake and kind of stall but never dies and the service engine light came on. I had a mini scan done and most things point to an MAF sensor. Someone else checked my original gas cap and when loosened didn't here the poof sound of pressure and they said maybe that could be it, or even an o2 sensor. Any ideas? Thank you very much.