Are you using the stock TB with the diffuser plate on the bottom? Check to see if the plate highly carboned up.
It is stock. Can you see that with air cleaner off or have to remove TB?

I'm doubting it, the intake gaskets and spider were recently done, not by me, before I got it. Very nice work too along with everything else, I have maintenece records since new, no expense was ever spared on care of this truck... but you never know?

It is EGR related as I can turn off EGR and no more Bank 1 fuel trim changes?