Could the screw be jammed on paint?
I adjusted one, and it wasn't that hard to turn, but it was in a van, so I never saw it.
Restricted fuel filter or crushed tailpipe? Banks specifies 3" minimum.
Every bad Stanadyne pump I've driven had speed control issues, or wouldn't go over idle.
Did it sit or gat bed bad fuel, I've had a few cars that sat and were slow as hell for the first few tanks/filters & good additive. Marvel Mystery oil seems to work great, esp since its $2 at my local dollar store.
Does it rev to 3K no problem?
I've had 7 and 8(I think, definitely 1 blade different) blade compressor wheels on my 6.2, and as far as I can tell, it made 0 difference.
The EGT gauge in my Burb doesn't go below 300 either, peaks around 900 runs up to 8PSI, doesn't smoke(I'm not too confident in the gauge).
None of the Banks sidewound trucks I've driven smoked much. A fresh 7.3 with 4.11s in a van is fast enough you have to worry about crashing. 3.55 gears are quite a bit more lethargic.
I have the 7.3 manual in .PDF.
It should be just as fast as an OBS Powerstroke or F250 with a 351.
^Well there is some random info, if you come up with a specific ? I might do better.