Here I've a problem: when dessending in FLCH mode with throttles in idle  if I decrese speed in the mcp the airplane attitude changes taking up the nose and decreasing the -V/S value and that's correct. The problem is that the Auto pilot should maintain a descend attitude even if decreased in order to permit the speed to fit the input given to the mcp; the 757 of captain sim decrease the descend attitude while slowing down but then it starts to climb!
I guess this is an incorrect behave of the CS bird... I belive that the real 757 keep on descending in FLCH mode even if the pilot decide to decrease the speed in the mcp!