what should fuel psi be at the rail and the specs for leakdown and can u check it with just a normal air psi gauge, and must it be running or just the key on

 

What vehicle? What engine?
Engine running to check static and the momentary increase when throttle quickley opened.
No, get a proper fuel gauge with fittings.
DT

 

91' 302. Approx. 40 psi & should hold fore a while after engine is shut off. There's a more involved specific procedure/ #'s, involving the fuel pressure regulator, but it's been so long, I'd have to look it up. This quick n' dirty method is "usually" good enough for a stock setup, to point to a problem.