We get questions on a fairly regular basis, asking about the importance of a fuel pressure gauge. What we say is that the main desirability for having a gauge is the ability to monitor the function of your lift pump and monitor the fuel flow through your filter.
As a pump wears, or a filter becomes blinded doing its job, the pressure will normally go down. If you monitor your pressure as you drive and are used to a normal operating range, then when it goes out of that normal range (similar to an overheating engine temperature gauge), underperforming fuel pressure can be caught and diagnosed before causing injury or damage to the injection pump.
We are always happy to discuss any of the issues you have as a result of your fuel pressure gauge and welcome questions for procedural information should you have any concerns.