My 5.3 recently started to run really lean it drove like sh*t under any load or high rpm. I found it to be that my fuel pressure was low so I pulled the bed off and found the hose clamp came loose on my Walbro. So I replaced the hose with submersible line and it fixed the problem, it ran awesome! BUT after a week the problem came back. Now it is even worse. I have not put a fuel pressure gauge on the rail yet but i am soon. Sometimes under light acceleration it will suddenly have a extremely lean spike really fast, so that might be a clue. I'm trying to narrow down my possibilities but nothing is coming up.

Im thinking maybe the ls1 FPR may be bad or maybe the pump or just the connection again. Pretty sure the injectors are fine

also i may have a small vacuum leak and the pcv system is kinda a working process. Ive been trying to try different things to see what works best but the problem came before I touched the pvc set up. So those things may also change the afr

Please help me I'm despite at this point lol!

The truck is a 2007 classic 5.3 flex fuel with a Ls6 intake stock ls1 fuel rails with a FPR on the rail. Walbro fuel pump. FBO. Cam.