Mine came on whilst it was still stock. (it s not stock anymore!)
They needed to re-program the ECU - apparently not a problem, just a poor tolerance in the software. After much prodding I found out that they(my dealer alone) had already had 25 of these come back like this.
You will get a **** rental car, but it is done for free under warranty. They have to send your ECU back to Subaru to do the job though.