I have a problem with my 4.8. It has what feels like a miss fire as you accelerate but seem to get better after 30mph. No codes and I have checked the plugs and replaced the wires but no help. I am leaning toward the fuel pump, it is an inline rated for up to 70psi and 60 gpm. With a pressure gauge hooked up I am getting 60psi at idle. Any ideas or suggestion on what might be the problem. It has a rough idle. Thanks in advance.

 

Log your AFR during that time. Possible lean-out condition?

 

I will look in to it. Thanks