Originally Posted by cenix
Thanks for sharing. I'm hoping Cobb Tuning will chime in with some possible insight.
The ECU's ROM image can change after the vehicle is released as Subaru makes updates/fixes. Those updates are supplied to the dealer who will reflash a car if it exhibits the problem solved by the update (or for all cars if there's a recall). The dealer can read what ROM revision is flashed to the car and if it is newer or older than the one that came on the car (and there's no record of the dealer flashing another ROM), then they can assume that someone has messed with it. So, likely, when the previous owner put the stock map back on there, he didn't use the original one that the car had.
With the AccessPORT v2, it will back up the current ROM when you install. When you uninstall the AccessPORT, it will flash that backed-up ROM and therefore return it to its original state.