I'll third that comment..

 

The original question. If the 6v92 is manual fueled, bigger injectors, timing can be adjusted to some extent with the injector setting. Back them out it smokes more and so on. If it is a calif truck the cam timing can be advanced 5 deg to get it up with the fed specs. That gains 20 hp. To get serious it needs the intercooler if not equipped. The liners can be replaced with export liners that have .100 higher ports. This listed will make it tear up a 350 cummiins on a hill.

Don't open up the fuel returns as was suggested it will only lower the fuel pressure at the injectors, smaller would do more but for more steady fuel, use a 12v71 fuel pump and use a return jet from each head with two return lines back to the tanks, cooler in the summner and hotter in the winter.

Make sure the fuel lines before the pump are good, they can bleed air in the system dramatically losing power. In this condition they will not leak fuel, just air in and was a common plague with the detroits.