I am a new mac user and I got my new macbook air (i5,8gb ram,256gb) two weeks ago. I downloaded tf2 last night and tried to enjoy the game, but it was lag and fps was about 25~30. (In the mid performance setting) Most of the reviews show that even in max performance setting, tf2 can still have 50~80 fps. I have no idea about Mac OS, can anyone help ? Thanks.