Update

Just a quick update concerning the "backfiring of my 07 malibu: I went to the dealer and was toldthat the car wasn't throwing codes and that I "needed" the 12000 mile servicing for about $700,00. I politely declined. I was then told that I could "get by" with a simple injector cleaning for about $300.00, that I too politely declined. A mechanic there then took me aside and told me to get a bottle of Chevron (techron) injector cleaner for about 5 bucks, and that would do the trick. The results are in: The car now runs beautifully, like new! Thanks Chevy for all your help