Have a 1988 GMC K1500 5.7. Was driving one day, bogged down and would not start again. Acted like there was loss in power. Replaced the fuel pump and fuel pump relay and still no fuel. I have spark and tested the pump and relay to make sure and they are getting power. Not sure if the injectors are bad don't know how to test them. Also replaced all the fuel lines, filter, and the fuel strainer. Please help!!!!!!!1