When you turn up the pump on a diesel engine you are changing the maximum fuel setting. to do that on a inline multiplunger pump as used on the M4950 you adjust ( increase) the rack travel. The screw that you turn to do that on the M4950 is on the engine front cover directly ahead of the injection pump. You would turn it counterclockwise (out) to increase maximum fuel. Should you do it? Well, it is set where it is for a reason! I would make sure that everything else is right ( valve adjustment, injection timing etc.) before changing the fuel setting. Even then, you might get a satisfactory smoke show out of it and not really much more power! If it had a turbo........
The limit on HP with a turbocharged diesel is when something breaks or melts!
Ed