You probably want to get the code scanned so you know what the cause of the CEL is. (Go to AZ or a Pepboys type store...) Many CAI's for the Mazda6 will throw a CEL due to the MAF tube being larger than the sensor was calibrated for. Some other key things to look for are plugging any loose...
What kind of bulbs are you using? I've had poor results with the Silverstar types (Same as Osram bulbs I believe...) but they have been good for 6-7 months. You might want to stop by an AutoZone or similar store and get your charging system checked out. It's possible your voltage regulator (Part...