try to run a fuel pressure test on it. alot of time when fuel pressure is too low you wont get adequate jet spray, but when primed like manually inducing fuel the jets will open allowing fuel to pass. apply power and ground to your jet. if it functions correctly i would look for a bad ground or frayed wire to jet/injector. otherwise, you may also have a clogged fuel filter,line, or jet. i have seen many new fuel pumps lack adequate pressure, especially with aftermarket pumps. i always recommend ac delco pumps in all gm makes and models.