misfire on 4-5-6 bank after replacing head

[Coaster]

Thank you all again. The issue was related to timing bank 2 with the UDP installed. There is a mark on the UDP pulley they were using for timing and it is not quite aligned with the original pulley. Once the UDP was replaced with the original pulley (which I keep in the car tool kit), the cam time was off. They did pull the motor mount and drop the front of the engine a few inches to redo the cam timing on bank 2. It's been a week since I got it back and no CEL and the gas mileage has gone back up.

[Gelbster]

" The issue was related to timing bank 2 with the UDP installed. "
Just Bank 2 ? Not Bank 1 also ?
Both Banks are timed at TDC Intake/Exhaust for Cyl 1 so how is only Bank 2 affected?
When they timed Bank 2, they automatically re-timed Bank 1.
Note the new UDP was probably missing the timing HOLE - so it is impossible to lock at TDC. That may have caused the issue?