I have a 96 dually with a 454. The truck runs great and will pull anything. The problem is after driving the truck for more than 30 minutes it will not start. The check engine light is giving codes 171 and 172 , right and left bank running to rich. After sitting the truck starts fine and off I go. The truck has 94k on it. I have been told it is fuel regulator, along with many other things. Cost wise, I would appreciate a guess if this is the problem. Thanks, Barbara