To be honest I run on 95 octane, never had any problems, it depends what fuel the software is written for, as standard the 4x4 was unleaded (This is what the green cam cover denotes, assuming YBG) to get back to standard you ideally want a standard chip,you may need to wind the boost down a bit as well.

It depends on the D/V as standard they have a Bosch recirculating item, if atmospheric then it's been added

Correct that is the standard boost pressure, and if this is exceeded they will hit overboost protection, I do know the exact strategy but won't bore you with that

Martin