How are you supposed to figure out a PC githzerai's stats? There are no stat adjustments in Manual of the Planes, and there's no mention of them in Savage Species. And yet, they're ECL+2.
... and spell resistance and spell-like abilities. They're worth their +2 ECL which I have confirmed by playtesting
As for figuring out stat adjustments, if the normal score is an odd number subtract 11 from it to discover the stat adjustment; even scores require that you subtract 10.