I have a 2001 Ford F-150 5.4L. It has 150K on it. Sometimes it wont start, and sometimes when it starts it runs rough. I think its fuel related. I did a pressure check on the fuel system. With the key on I have 8-10 PSI, when it runs I have 30 PSI. I have already changed the filter with no change. Should the pressure be 50-60 PSI? I dont wont to change the fuel pump just for recreational maintenance, if it could be something else.... Thoughts?

 

From the shop manual:
Fuel Pressure
Engine running kPa (psi) 193-310 (28-50)
Key on engine off kPa (psi) 240-310 (35-45)