Discription of Events: All I know is that were going a solid 76-78MPH as the speed limit is 75MPH and this driver comes FLYING up towards us from the right lane but is forced to slow [RAPIDLY] from what I will guess 90-100MPH at a rough estimate. Gets behind us quickly, no blinker and gets right on our tailgate. Eventually turns around us and speeds up again and turns into an exit before 118.