ecu's are often locked to prevent you going else where having it altered or altering it yourself blowing it up,then returning it back to the original tuners map and then blaming him for the blow up
why didn't your mate take it back when it ran shite after mapping,or was it ok and has developed a run fault
surely you would have noticed it was not running right when you bought it and reduced the purchase price, or do you just like moaning roflol