98 350 vortec 5.0 liter

see if the injectors are firing normally unless you have the TBI unit on top the motor then just see if those injectors are working ,, , test or replace ignition module , and if you can purge the fuel rail at the valve see what the gas looks like , check plugs , wires ,coils , I used to think parts (alt. fuel pumps ) ,would just quit but thats not always the case ,intermediate problems are the worst because the problem has to be tested when it occurs otherwise it'll test normal , a gas soaked rag is asking for problems get a soda bottle with a pin hole in the cap and squirt some gas in the throttle if you have to ,