Ok, It definitely was NOT my TW chip! The problem persisted, then...
2 years ago I bought locking gas caps for the truck when diesel hit $5/gal.
They were not for a diesel and there definitely IS a difference.
I drilled 1/4" holes through the gas caps, converting them to diesel fuel caps.
WOW what a difference it makes when the tank is not under a vacuum.
It even runs better in stock mode!