I Know this is an old thread but I decided to update it just provide helpful info. Two things were going on with my Xfire. I had changed the fuel filter but the new filter was clogged, I found this out by taking it out and blowing through it. I had changed the MAF a few months ago when the car was hesitating but it was with a Cardone MAF, I decided to remove the Cardone MAF and changed to the Bosch OE and Whola--the Xfire runs fine and no more CEL