If you have a plan of attack you don't need me to inject anything to confuse you.
If in case you don't , maybe I could offer a suggestion or two that might save you some time and unnecessary expense.

 

now that you have it running I suggest disconnect the negative battery cable and touch it to the positive to clear those codes and if it still throws the codes then something went wrong somewhere but it doesn't hurt anything to try that first. if it works then problems are gone, and it didn't cost you nothing but your time and labor

 

I'm open to suggestions. The problem I'm facing is that the truck is still misfiring and losing power.

 

the problem you have is that the fuel pressure is just enough to get it start but not run normally. did you ever put a fuel pump in the tank or switch tanks. I just reread the entire post and I didn't see where you followed up on the fuel pressure problem. I hope that you checked the fuel pressure again and see if it's still just puts it up to 20psi if it is then you'll have to replace that pump. there are two ways a fuel fuel pump goes bad one is that it quits all the way around and doesn't work at all and the other is that gets weak over time and use and doesn't get the fuel pressure up enough to run normally meaning that it gets just enough to start but can't maintain the pressure to make it run smoothly

 

Would it also. cause the misfire?

 

You know at this time you're vehicle has a fuel pressure problem. Whether it causes a misfire or not is secondary. Before chasing anything else you must correct the fuel pressure problem. Taking things one at a time will eventually get to the bottom of the problem(s).
Grindman suggested that you clear the codes and run it again to see if you got the same codes. I agree that is good advice. As stated earlier, if you have a plan of attack, good !
Do you think you would care to share that plan and see if there is something you could have overlooked ?
I do have some questions that you could maybe answer up the road, but you do need to do first things first.

 

Agreed. It will take me about a few weeks to get paid again so I will get the pump then.

 

A lot of us here read the posts and watch to see what solves the problem. That's how we learn. Please keep us informed when you get back in gear, OK ? Thanks

 

After 2 hours and 13 dollars later I took the intake off and replaced the gasket I believe is a plumens gasket or something close if I mispronounced and used silicone to seal it. Also saw that the pcv hose was lose anyways so I just cut it in half and sealed it with a bolt in both sides to block air flow. Then I reset by way of battery cables and started the truck. Misfired right away and I left it running. Unplugged the idle air control and plugged it back in after a minute. The truck roared with power and and smoothed out life it was new again. The I repeated the idle air control step 3 or 4 times and the computer reset it. After repeated cranks now waiting for cold starts and all it has no miss and no delays on starting and no rough idle. No loss of power. And best of all no new 180 dollar non refundable fuel pump. Fixed diagnosis was air leak through intake due to bad gasket and air leak through bad pvc hose. It has positive crank ventilation through other means so blocking the hoses like I did did not affect the other sensors.

 

you're still going to have to replace the pump sooner or later, another thing that you'll need to do is change that pcv hose and let it vent the right way cause it will eventually cause something else to go wrong or make it run rough again and throw another code. but glad you have it running smooth again. the 4.9 engines are known to last a really long time as long as they are maintained well