The fuel screw is set while the pump is on the calibration machine. There is no "factory setting" as each pump calbrates just a little different. Just like the timing mark for the IP on the gear housing. That was set at the factory when the engine was built and was adjusted during the test run on the factory line when they were being bulit at the IH Plant in Indy. If you took the pump off the engine that it was built with, that mark is correct. Once the pump is rebuilt, even if you have the factory pump rebuilt, that mark on the housing is no longer correct. It then has to be timed with a meter and adjusted accordingly.
I'm with IDIBRONCO, back it off, drive it, back it off, drive it and get it to where on a hard acceleration it get just the lightest haze you can see, like can only really notice unless it is at night and you catch it in the headlights behind you. You don't want a ton of smoke, because this will drive the EGT's up, and is a waste if money. Any black smoke is unburned fuel that is not moving you or your load down the road. But, it is possible to turn it down too far, and limit fuel and take away power. If you have no smoke, and feel like the power is down, then you may have to turn it back up a bit. When you adjust it, keep track of how many "flats" you turn allen wrench. Most of us here refer to adjusting this screw in "flats" (I.E. - Turn it up 2 flats, or turn it down 3 flats, just so you have an exapmle). That way, if you turn it down 3 flats, and notice a power hit, then turn it back up 1.5 and see if it comes back. That will let you know how much you changed it, and if troubleshooting is needed it can help us, to help you.
