I have recently bought an 03 3500 dually from a very good friend that has lots of experience with diesels. The truck started surging at idle and is real bad when in gear only while stopped, but it runs great as soon as your on the throttle. We have replaced the FPR twice with no change, while watching the truck on the computer everything is great all injectors are well within spec and fuel pressure is dead on. The only time the surging goes away is when the truck is warm most of the time or if we are to pump the fuel primer but we have re-oringed the primer. Any help or suggestions will be much appreciated! Thanks