Here are a couple of pics showing what has changed if you want a visual. The first is the actual ignition timing. The second shows the difference between the base 91 octane base tune and the lean-burn 87 octane tune. The positive (red) values show where ignition timing was increased in the lean burn range. The negative (yellow) values show where ignition timing was decreased allow for 87 octane fuel.
Ignition Timing
Ignition Timing Delta
There are coarse knock learning tables that define how much ignition timing is retarded after knock events. I used these tables as a guide for determining how much ignition timing to pull, then fine tuned the values a bit based on knock readings during driving. The software used is Accesstuner Race.