Hey guys, so I uploaded my tune from American Muscle last week, and things have been great. Better fuel economy, no more CEL from my x-pipe, and smoother power delivery. However, not five minutes ago, my CEL came on again. It seems to coincidental to be something else on the car, and I'm thinking my O2s went back to thinking I have cats. Not sure at all. Any ideas as to why it would have come back on? Does this usually happen? Thanks in advance guys.