2000 Chevy Trailblazer fuel pump psi rating?

I just replaced the fuel pump, filter, and relay on my girlfriend's 2000 trailblazer. The filter was definitely clogged which I am guessing caused the pump to burn out. I could not find just a pump for sale, all the parts stores wanted to sell me the complete sending unit with pump included for $319+ I got a pump only from napa for $42 but it is for a 94 blazer. The pumps look identical, and the guy at the counter said they both have the same psi. I was told by a mechanic that on the newer trailblazers, if there is not enough pressure that the computer will not allow the fuel injectors to work, is this true? What is the recommende psi for a 2000 trailblazer? Everything has been hooked up properly, there is pressure in the fuel rail, the pump works, but fuel is not getting to the injectors. It starts if I dump some gas down the throttle body and will run untill that is burned off. Is there something I am missing like maybe a reset switch somewhere? All the fuses are good, and the pump is working great, just not the fuel injectors. The "spider" as ive heard it called does not leak, so I doubt that is the problem. Any info would be greatly appreciated, I am totally stumped on this one. I should also add that the truck has a 4.3 V-6 with the W code in the vin#