Black to play: what's the best move?

GM Dmitry Gurevich - Michael Auger, 2009 Illinois Open, Black to play 

I was playing on the board next to Michael Auger when he uncorked an amazing move that forced GM Dmitry Gurevich into a 45-minute think.  Gurevich managed to win a very dubious position: look for his annotations in the Illinois Chess Bulletin, going to the printer in the next few days.

To find out what Michael played, please see the previous post.  (And if you have any problems with the embedded PGN viewer, please let me know.)

If you have any last-minute submissions, please send them to me now!