Hi Gerald,
As normal around here we'd all suggest you put in some guages before you go too much further... .
They will actually tell you alot about exactly what you're asking... .
The amount of fuel you can apply is related to the exhaust gas temperatures you have. There is a generally and well accepted max exhaust gas temperature (EGT) that you can safely run... that temperature is 1250*F.
The fuel screw will send more fuel to the entire RPM band on these trucks and will start to raise you EGT fairly quickly as you increase the fuel and work load so use some care until you can at least put in an exhaust gas temp gauge.
Also keep in mind that the transmission(s) are able to handle a moderate increase in HP but will begin to cry and snivel if you go too far.
For now, let it be until you can get some gauges.....
I hope that is some help ???
For a more detailed explanation try looking/reading the first two or three topics (sticky's) at the begining of our section. They contain alot of "how to" information.
bob... .