I have been trying to resolve a low group head pressure issue since I got my used machine. I have attempted to adjust the pump pressure and have replaced the group gasket. I think my process of elimination leads me to the pump itself. Its putting out only about 40psi. I am looking for a replacement. The pump that is in there is rated for 35gph flow and preset to 125psi. How important is it that I maintain 35gph? I see more pumps rated at 100 (I have yet to find a 35 available for direct purchase online). Most also seem to be preset to 130psi. Where can I fudge in making a selection so that I still get a pump that will function?