My car is an 04. the CEL actually is on but has been for about a year. It was brought into the dealer last year i think and they said the CEL was just due to a sensor issue and the wanted 400 bucks just to disable it. I always run 91 actually but not sure if the previous owner did. As far as plugs go im not sure whats in there now all I know is that they have only been changed once maybe. The issue hasnt happened this past week but it definitely gave me a scare when it happened.