Voltage offset would be covered in the setting up a wideband how to if I'm understanding what you are asking.
You'd change the second part of the formula to adjust for whatever delta you're seeing
http://www.hptuners.com/forum/showth...l=1#post416605
Instead of 0.72 you might have 0.74 or 0.68 to account for a voltage offset in picture below
Or if I am misunderstanding then give more detail and I'll try to help.