2006 ISX CM870 High Pyro, surging under load

[sickoftrucks]

We ran the injector test again with insite. It passes. We did find a blown 10 amp fuse for the lift pump. The pump now works, but nothing changed. We also found the fuel is black, can't see through it, but no oil consumption that we know of. I just drove the truck again. It runs well until you give it throttle over 1500 rpm. then it surges, meaning power is not steady. Pyro goes up fast to 900-1000f. it is pretty gutless as well. No smoke except a small amount when you shift and step on it. last item, there seems to be no 3rd stage engine brake.