It's been awhile since I've worked on an OLCC machine but some other things are coming back to me. Turning the pumps down should let you run the machine in S mode without killing the engine. The responsiveness may or may not come down because your system does not have jet sensors in the main control valve that would give you that true load sensing function. If you get it so the pump doesn't kill the engine, then check you cycle time by extending the stick all the way out, opening the bucket and sitting it all down on the ground. With your engine at full throttle, raise the boom all the way to the top and time it with a stop watch. It should be able to do that in about four seconds. Make sure you keep track of how far you turn each screw in case things don't work right. The machine is probably workable to some extent right now if you have to put the adjustments back. Also keep in mind that you have an old machine and the control linkages might be stuck and need dismantling, cleaning and new seals. The two small screws adjust the actual pump hydraulic load control valve which shown here. The larger adjusting screw adjusts the pump reaction to the output and pressure on the pump. This is to limit the output of the pump to less than the horsepower of the engine.