after you get the new plunger installed successfully, look carefully at how fast it reacts when you move the throttle (you can do this on the workbench). That is what the 3 different holes are for on the pump arm. The adjustment can also adjust the pump stroke (longer stroke, more gas), but at the same time, the plunger needs to start moving instantly when you touch the throttle. If there is a lag in the plunger movement, it will show up when the engine is running as a slight bog when you tip the throttle.