First. If you are running a 13 hp engine it is physically impossible to get 4 at 4000. How much hose are you using while setting unloader? Pressure gauge should not br used when setting unloader. Never start machine unless trigger is already pulled when installing new unloader. Pressure is irrelevant. Set for max flow and pressure is what it is. Adjust unloader until allow about a drop a second is running thru bypass. That’s it. You’re done. 4 at 4000 is like pressure pros selling 8 at 3500. False advertising
