[CAGRacing]

Don't pay someone for a live fuel pressure feed. I was a mechanic and all we do is take off the engine cover and connect our mechanical fuel pressure gauge to the shrader valve and drive the thing. save your money.
I'd check pressure first then grab a bottle of brake parts cleaner and a roll of shop rags.
Clean the throttle body, pull the egr valve and clean it out. then reach as far as possible into the intake
if you don't have cash for injectors pull them out, remove all rubber and soak them in acetone over night
You'll be amazed what it'll remove.
Oh and when I said a can of brake parts cleaner I mean a case.
A lot of problems with new gm motors are traced back to carbon build up and intake gaskets.

But I'm new here so don't take my advice as Gospel.