My pressure washer is a 3500psi 4gpm belt drive cat pump on a 13hp honda. I mainly do driveways and sidewalks using a 18 inch Surface cleaner on a 200 foot hose ( and I routinely need more than 150 feet out so shortening the hose is not an option) but I think I would be a little more efficient if the pump could put out 4000psi. That should keep me up around 3700 psi at the surface cleaner instead of 3200 psi like it is now. I don't have the model # of the pump handy but my question is can a 3500 psi cat pump be converted or adjusted to do 4000psi? Or will I just have to buy a new pump? It has a flow actuated unloader on it.