I would just look into renting one of the fuel pressure testers, no point replacing it if its accurate. You should be able to rent one from local auto part stores like autozone or orileys. If you cant get one, I would look into getting one from harbor freight or amazon. If you already have a gauge on the rail then you already have the adapter you need to connect a pressure test kit.I will invest in a new gauge it is pretty old looking.. what are some recommendations? I will let you know if I see anything when I get a chance to jack it up.