If the gauge is slow to respond going up it can be slower going down, or not go down at all under load so that needs to be dealt with to get an accurate picture of the fuel system. Does the gauge drop 5 or 10 PSI instantly as soon as the pump shuts down? More than once were the OP has not done a fuel pressure test before and doesn't know what things should look like get fooled by the gauge/connection. +1 one one the smoke tester, not the most reliable way to prove no vacuum leaks me thinks
++ fuel pressure test includes driving under load with the gauge taped to the windshield, again common thing for a DIY'er to be fooled by not doing properly.