Your engine RPM seems a little low to to me. You should be able to safely spin to 5300 RPM. I would think a prop change is in order. Something that takes a smaller bite would lighten the load on the engine allowing it to screw itself farther through the water for more boat speed. Consult a prop guru!
As for changes to improve engine performance, please remember that the fuel map in the ECU will have to redone. Some times this is a long trial & error process. The model of ECU will determine who can do it.
Hope this helps.