During the Fox broadcast on Saturday, Joel Klatt said that, "every time a Michigan WR goes in motion it's a run play, when they don't it's a pass play" Of course, after that comment every Michigan fan watched as a WR went into motion and Michigan ran the ball.
People that have more time than you or I do will watch tape from every Michigan game this season and come up with the data if this is true or not. Brian at Mgoblog has a theory that every time Michigan is in the Pistol, they run the ball.