Maybe coincendence but immediately after I replaced my stock muffler with a magnaflow. No more check engine light. And that check engine light has been on for 9 months since the day I owend it. Could have there been a problem with the stock muffler causing too much backpressure to trigger the the check engine light? Paritally collapsed stock muffler maybe?

 

Could be very well be. IT wouldnt be the first time i have heard that. Sometimes a compromised muffler can cause to much back pressure to the point where the SES gets triggered, A similar thing happens if you roll down a steep hill with the car in first (M6) and it gets to point where your wheels are turning the engine and not vice versa, Just happy to hear it was a simple fix.