CS8804

I have a 03 GMC Sierra and have a slow drop in pressure as well. 55 psi to 20 in about 20 min. I too have to turn the key twice to get it to prime. Thought it was okay since it’s a theft deterrent but now I just want to fix it. I found that I had a leaky injector, so fixed that and hooked up gauge and it now more slowly drops psi but still drops. I replaced pump and did that splice connector thing and it still drops. Changed fuel filter and old one had a bunch of black stuff in it. I also changed the fpr. I think the fuel pump still might be the problem. I also get get a code of P0446z I read from another thread that the pressure sensor in the fuel pump was giving that code. The thread also stated the guy replaced pump again with a different one and all his problems were gone. I tested the fuel pump directly and it gave me a really high pressure over 60 psi then slowly dropped but the gauge connection was leaking. I’m at wits end to figure this one out.