Stock files are available (for purchase/loading) and strategy codes are not often specific to an individual vehicle, but rather a bank, or grouping of vehicles.
My biggest concern in reading through this, is the fact that the previous owner has (what is believed, or reported to be) a working key to the current owner's car.
That's a big no no, and the fact it was kept, and now this previous owner monitored the sale of the car, and reached out to the current owner immediately after purchase, is a tad bit disconcerting.
I would be HIGHLY SUSPICIOUS of any/all of this personally.
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