^^^That is some nasty lookin soup. Bet its been sitting for awhile. No doubt you have/had quite a bit of algae cooking. Here's where I'm at considering what you've done and replaced: you need to flush the entire fuel system out.
Do you have access to an air comp? I'm guessing you have one.
Start at the tanks. Is it still a cab/chassis? If so, easy enough to pop both senders and look inside both tanks with a bright light. If there's crude or blobs of milky looking snot, both tanks need to come out and thoroughly cleaned and flushed. Then add some algaecide with fresh fuel. Myself...I use Kill-em with excellent results. I use to use Power Service Bio Kleen, but prefer Kill em now. If there's minimal cloudy fuel in the tanks, you might get away with just the algaecide. But there's still a risk. Also be sure to clean and blow out the sender pipes as well.
Next I'd disconnect the lines from the cooler and blow that out. Pay attention to what comes out by using some paper towels or a light colored rag. Then disconnect the fuel lines at the filter under the hood. Blow them while the cooler underneath is disconnected. Try and capture what comes out, but its not critical since you said you replaced them. I wouldn't worry too much about the filter itself other than maybe draining it. You said you already replaced it a couple times.
Next disconnect the lines at the FICM. Blow that out and capture what comes out. Also blow the lines out if you can disconnect the other ends. Kinda tough to get the one at the pump, so don't sweat it if you can't.
Last but least, and the most dreadful to do...for me anyway...pull both rails. Be sure to capture what comes out of both. I suspect you're going to find some junk, since that press sensor had that crap on it. Pay extra attention to flushing out both rails...fill them with Brake clean and shake like hell a few times until the Brake clean drains out crystal clear. Then blow them out. Also blow out all the injector lines since they'll be off anyway. Any other lines from front to the rear that you can access both ends, including the return lines should be blown out.
It's a lot of time consuming work, but with the problem you have, it needs to be done again. Reason being: GM had a problem with certain years pumps failing and sending metal throughout the entire fuel system. The repair and parts were covered by GM, but soon after they started this special policy, they cut the time in half...from close to 30 hrs to about 12. Pissed off many guys who in turn, took short cuts with the cleaning. But that backfired, and the same problem they were originally fixing, came back to bite the in the ass. Tech ate all the labor 2nd time around and the dealer ate the parts...which were major $$$$. Since you didn't clean the entire system the first time, I think it bit you in the ass unfortunately.
**I edited this a few times to clarify, add info and correct errors. And to say: this fuel system is a quirky setup and you'd think the filter would catch everything, but it doesn't. I can walk you through the bleeding process afterwards, but I doubt you need the help since you went through it already. Let me know if you find any crap blown out. Or I can probably stop by at some point.
Do you have access to an air comp? I'm guessing you have one.
Start at the tanks. Is it still a cab/chassis? If so, easy enough to pop both senders and look inside both tanks with a bright light. If there's crude or blobs of milky looking snot, both tanks need to come out and thoroughly cleaned and flushed. Then add some algaecide with fresh fuel. Myself...I use Kill-em with excellent results. I use to use Power Service Bio Kleen, but prefer Kill em now. If there's minimal cloudy fuel in the tanks, you might get away with just the algaecide. But there's still a risk. Also be sure to clean and blow out the sender pipes as well.
Next I'd disconnect the lines from the cooler and blow that out. Pay attention to what comes out by using some paper towels or a light colored rag. Then disconnect the fuel lines at the filter under the hood. Blow them while the cooler underneath is disconnected. Try and capture what comes out, but its not critical since you said you replaced them. I wouldn't worry too much about the filter itself other than maybe draining it. You said you already replaced it a couple times.
Next disconnect the lines at the FICM. Blow that out and capture what comes out. Also blow the lines out if you can disconnect the other ends. Kinda tough to get the one at the pump, so don't sweat it if you can't.
Last but least, and the most dreadful to do...for me anyway...pull both rails. Be sure to capture what comes out of both. I suspect you're going to find some junk, since that press sensor had that crap on it. Pay extra attention to flushing out both rails...fill them with Brake clean and shake like hell a few times until the Brake clean drains out crystal clear. Then blow them out. Also blow out all the injector lines since they'll be off anyway. Any other lines from front to the rear that you can access both ends, including the return lines should be blown out.
It's a lot of time consuming work, but with the problem you have, it needs to be done again. Reason being: GM had a problem with certain years pumps failing and sending metal throughout the entire fuel system. The repair and parts were covered by GM, but soon after they started this special policy, they cut the time in half...from close to 30 hrs to about 12. Pissed off many guys who in turn, took short cuts with the cleaning. But that backfired, and the same problem they were originally fixing, came back to bite the in the ass. Tech ate all the labor 2nd time around and the dealer ate the parts...which were major $$$$. Since you didn't clean the entire system the first time, I think it bit you in the ass unfortunately.
**I edited this a few times to clarify, add info and correct errors. And to say: this fuel system is a quirky setup and you'd think the filter would catch everything, but it doesn't. I can walk you through the bleeding process afterwards, but I doubt you need the help since you went through it already. Let me know if you find any crap blown out. Or I can probably stop by at some point.
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Told ya I'm guilty of speed reading. Bad habit from the flat rate days.
LOL I will admit some is my fault, I am Dmax dumb but I know more about them now. Plus lesson learned.... don't buy fuel injection parts off ebay.