@ Gevo - I didn't think to check that, no mention of checking PSI at throttle in the FSM just at idle, but I probably should have, makes sense to just see what it does. Already got it disconnected. I just ran it 30 seconds or so - long enough for the test cause I didn't want to open the garage door. It did pass the leak-down test though. Made it almost 30 minutes before it dropped down to 21 psi. FSM says 5 minutes.

@ AxleIke - The coil passed the ohms test.

I'm switching out the MAF sensor just cause I have another one, even though the one in the truck passed the FSM tests. WTF else is a muther to do, besides have another Sierra...

 

Looks like you are doing everything right and can feel your frustration. I havent used a pressure guage in years, but on the fuel, what I do is pull the Return line off of the back and with it running or the Fuel Bypass jumper on it will fill a quart jar in a minute or so and usually works great enough to let me know if it is getting enough fuel.

 

I may have read it somewhere else, not the FSM, but I tested my fuel pressure with some moderate throttling. The idea is, if the fuel is being restricted somewhere along the line when you put a demand on the fuel system by throttling the engine, you can see the pressure drop. It should go no lower than 41psi (i believe this was the lower limit) at any time. HOWEVER, remembering back you had mentioned your problem is in a specific range of rpm, which means above that range the engine runs well (right?) and if so then the fuel delivery is less likely to be an issue.

I don't know what else to say at the moment. Let us know how the VAFM (not MAF, as I've learned ) swap turns out.