Gas in fuel injector harness

Could the gas be back feeding back into the harness from the first injector failure? If not, it sounds like the pressure regulator inside the fuel pump is bad and pushing too much pressure which is bypassing the seals in the injector but to be sure let's check the pressure which can be done by following this guide. Also did you use an AC Delco part?

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Also, I have included now to change out the pump in the diagrams below. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.