There is circumstantial evidence that he has the Metamagic Specialist. First and most obvious is that he does not have a familiar. Yes, I know that absence of evidence is not evidence of absence - thus circumstantial. But "Power = Power" Xykon is not one to leave a character bonus behind when it might give him an edge, so I find it unlikely that he would have forgotten he has a familiar; instead, he must have traded it in for something, and Metamagic Specialist fits (I don't know what other alternative exchanges exist).
The other circumstantial evidence is, I believe, the Maximized Energy Drain. I'm not sure of the details, but isn't there an issue with how this spell was cast that was explainable by the MM Specialist? At least, I can't imagine were else I would've heard of the concept.
Grey Wolf