Pop-off Testing is a major part of carburetor tuning. Having a pop-off gauge is important not only for measuring pop-off pressure but also to check leaks that can be coming from the inlet seat, inlet needle, carburetor diaphragm, and gaskets or the carburetor pump plates. It's critical that if you run a Tillotson or any other diaphragm carburetor, you have one or two of them in your toolbox.