What is proper fuel pressure

[patmac6075]

What is the proper fuel pressure for my '98 4.0 OHV?
Went to auto parts store and rented a test kit...my pressure was 28 ~ 30 psi both before and after changing my filter. Just seems a little low to me. Car was running fine beforehand (just routine maintenance)....I'd swear it runs better (much smoother) now with the new filter.

 

[2000StreetRod]

30 to 45 psi

Haynes states at idle your return type fuel pressure should be 30 to 45 psi at idle and 40 to 50 psi with the vacuum hose to the fuel pressure regulator disconnected.