I have a 94 blazer 4.3 cpi injection, truck has 60 p.s.i. fuel pressure when not started pressure starts to drop slowly within 5 min. is at 40 psi. when is running holds at 53 psi. which I know is slightly low. has good compression 150. each cylinder, fresh plugs ,wires , dist. cap & rotor button, new fuel filter. truck starts right up but when idle to 1/4 throttle stumbles bad then runs fine past that anybody have any suggestions before I change more un needed parts..............

 

It has to hold above 50 psi for 10 minutes. You have a leak - either the FPR or the check valve in the pump.

 

Thanx for your help......