I have a ford f800 with a 5.9 cummins the factory torque plate has been moved around numorous times I know. have slid it back to keep the egts low and installed a number five plate in the same location i still have high egts this truck is constantly loaded but even on the flats it crusies at 1150 to 1250 and i cannot keep them cool also i have factory air filters that are to restrictive anyone have an idea on which k&n would work on this application

 

I wouldn't use a k&n on a diesel they seem small and insufficient for the large amount of air needed by a diesel. Are you leaking fuel anywhere? May also be a turbo problem. The turbo cools the air going into the engine to make sure the fuel is burned more complete which leads to lower EGTs. A turbo will help greatly in dropping EGTs and also an upgraded intercooler can help. Does the truck have a stock exhaust? Your cat may be clogged but doesn't seem very probable. Definitely look into a bigger air intake for this application because you are moving much more weight than an F250-350 which means the engine will have to work harder and need more air to keep up with the fuel demands of the truck.