I have been working on a new injection timing calculator for a while now. It's easier to follow than some of the older ones floating around. The spreadsheets calculate the actual injector pulse width that is being used based on your injection pressure, injection duration and injection BTDC (%) based on your current timing. Currently, the spreadsheet calculates timing for the following Duramax:
LB7 & LLY
LBZ & LMM
LML
L5P
I will add others once I can get my hands on some stock files.
EDIT: v1.0.2 - fixed a couple mistakes with L5P calculator
EDIT: v1.0.3 - fixed missing column on LBZ fuel pressure table
EDIT: v1.1.1 - fixed problem with LLY-LBZ tables