I was checking the fuel pressure and these were the readings I got:

KOEO:36.5psi
Idle:constantly jumping from 36-42psi
Long term fuel trim Left:121
Long term fuel trim Right: 131
Vac line off: 44psi

I am pretty sure these look normal. I don't remember it jumping around at idle before. Any ideas? I included the fuel trims in case that might cause the pressure to jump around at idle but I doubt it. Could it be jumping due to vacuum changing? What would cause that.... valve adjustment?

 

The fuel pressure is being managed my the fuel regulator and it keeps it within specs. If it was bad it might cause it as well as the fuel pump. The vacuum source not functioning correctly can cause problems. If I am wrong someone correct me.

 

yes the pressure regulator is controlled by engine vaccum the LT4 Hot cam might be lopey enough to make your vaccum to jump around if it is then your pressure will jump around too it should be fine

 

You shouldn't be seeing that kind of changes (6psi variation) due to intake manifold pressure variations with the LT4 HOT cam. Misfires? Incorrect valve adjustment? Poor tune?

 

If the vacuum is jumping around or pulsing on a vacuum gauge, it might be a intake valve not sealing.

 

For any one in the future:
Fuel pressure was jumping around becuase vacuum was jumping around. Vacuum was jumping because I had my valves adjusted too tightly. I have 7/16 studs and new stock lifters so I had to go only a quarter turn instead of the usual half or more on stock lifters. Now I have a steady 15" hg