I've heard about this recently, through a google search. I'd just bought a "2,1" model myself, with 2x 2.66GHz quad core processors, Radeon 5770. I was guessing the 5770 was flashed, and made me think when I remebered there were only 3GHz Mac Pro 2,1 models. I had repeatedly asked the seller the model, and the serial/etc all are pointing to 1,1. Googled anyway, apparently it's a bit of a 'scam' going on. Anybody else heard of this? Added: it came with a build Os 10.10.5 and it seems a few boot files have been modified, it won't boot under anything else, black screen. Might try to SSH in and mess around.