From what I understand, the Original FOF had 4 trains. FOF could only operate three trains on its circuit. As a result of this, the fourth train was used for maintenance/service for the other trains. I believe that 3 of the original 4 trains were transitioned from OTSC to lap bars. Today, there are 2 trains that run on the circuit normally. The third train is used for service parts. If anyone has anything to correct, please feel free too.
Also, are their any obvios remains of Outet Limits during the ride