More than likely your MAF sensor is dirty. Did you happen to clean the Piping for the CAI before you installed it ? The inside of the tubing was Filthy on mine when I got it, Alot of polishing residues and dust and dirt from Manufacturing. I just ran some water through it and dryed it off, then installed it.
Anyway if you put it in dirty, the crap in the tube is gonna foul up the MAF sensor in a hurry and cause the ECU to throw a code. The best remedy would be to clean the MAF with some rubbing alcohol and Q-Tips the reinstall it and reset the ECU. That should solve the check engine light problem.