I have fabspeed x-pipes w/o resonators and have driven my car for approx. 6-7,000 miles with it and NO CEL... I wonder why? Didn't even use the O2 extenders you guys are talking about. Could it have something to do with installation? I mean it's not just plug and play. You actually have to cut the stock x-pipe out and replace it with the fabspeed one. I would be interested to know if the exact position of the x-pipe(positioning) has something to do with the CEL coming on. I've had 0 CEL issues thus far and I'm at approx. 11,000 miles right now.