Just to note, Rob Rauscher of Dynamic EFI gets a fair amount of credit for what we can do today with GM OBDI and tuning in general. Rob was heavily involved in making an inexpensive WBO2 controller available to anyone (before this a WB was thousands of $$) and he did a bunch of work to figure out how GM OBDI code actually operates. Rob then took it a step further and published what he found for anyone else wanting to learn.