Turbo timer.

[Niall]

Does it lock the ECU to just that car though, or does it brick it?

When you put the key in and turn it to dash lights on, the BSI checks the key and if its good, sends a signal to the ECU saying its ok to work. Once the car is started you could take the fob away and it will run fine. When you turn the car off and remove power from the bsi and ECU, the BSI automatically sends a lock signal to the ECU. Thats why all the GTi guys pikey unlock their ECUs by removing them with the engine running. It doesnt receive that lock signal so stays working so no it wont brick it but if you were to take the ECU off your car whilst its running, move it to another HDi it would start but as soon as you turn the new car off, the BSI will send the lock signal and its locked in again to that BSI