1990 S-10, 2.5L starting problems

Maybe you folks can help me with a problem. I have a 1990 S-10 2WD, 5spd, 2.5 L 4 cyl, 105,000 miles. After sitting for awhile (a few hours to overnight), it won't fire up! I've changed plug wires, plugs, distributor cap, rotor, fuel filter, air filter, oil change. It will start if I prime the throttle body fuel injection with carb cleaner! When it finally runs, it will stay running and even start up after shutting it off for just a few minutes. This all started one day when driving where it started bucking real bad, then smoothed out. Then it would quit and I would have to prime it again and it would start. It seems like it loses fuel pressure over time, but once I get it running with carb cleaner, the fuel system stays pressurized enough to keep running. Any thoughts or ideas would be greatly appreciated!

thanks,

rilla

i would guess either the the fuel pressure regulator or if there are any vacuum lines that run to the regulator, check those. and all vacuum lines for that matter. also if there is a fitting, check the fuel pressure.