The truck is a 1986 model 1954/S1900 single axle 2 speed trans, with a DT466 that use to be a horse, now its a donkey. It has a R bosch inline pump. Its been running bad to worse for about 8 months now. It runs up to full speed/rpm then drops power & speed for a few seconds then back to full and so on. Stalls out when under heavy load in 4th and 5th gear shortly after it reaches max rpm.Now its starting to stall with no load. I never had any problems with it for the last 5 years I have worked it. Someone that I know told me that the new ultra low sulfer fuel is the cause, it eats the seals out in the fuel system on old trucks. Could this be true? It seem to make sence, because I never had a problem until I started running the new fuel. I Have changed the filters air & fuel, the water sep, the line from the tank to the water sep, the clutch, checked the pedal linkage,cracked all injector lines one at a time they seem to be ok,made sure all lines are tight, and still the same problem. It gets worse every time i use the truck. It Starts and runs good until it gets up to the higher speed & rpms. When its not moving and u put the fuel to it, it runs like a top no misses. No Smoke after it worms up,turbo sounds the same as always. Can Someone PLEASE HELP ME. I love this truck its like a child to me, and its the backbone of my small company. the IH dealer wants $1800.00 for a pump but I want to make sure thats what i need. I run my dozer, backhoe , and excavator on off road fuel and have no problems, and thanks to this web site and all of u, I have always been able to fix my own problems with out going to the dealer. I hope u guy can get me over this problem, and back to making money. the truck has exhaust leaks where it leaves the turbo and at the muffler. Also does any 1 know where to get manuals for these truck, other than the dealer.