Something else that occurs is that if the PO has put on Berks and an Invidia exhaust (perhaps there's even a plenum spacer in there?) then they may well have already had an uprev. If that's the case, and I understand correctly, they have paid for the uprev license, so if you found out which of the tuners had done it. They could confirm and you'd be able to get it remapped, disable the sensors and not have to soak up the cost of the licence.
It's a long shot, but it might save you and the customer a few quid. The list of Uprev tuners is quite short IIRC, Abbey, Horsham Developments, TDI North, RS Tuning. You could ring round and ask if they've upreved it?