Hi Pierre,
You'll need to provide more info about the car, for anyone to be able to help you.
It might be possible to virginize the ECU, you'll need to post the ECU details,( eg - Denso - 89661-05460.)
If not sure about immo box location/existents, the easiest way is to follow the wires coming out of the ignition coil (antenna).
If there is no immo box, then syncronization is not needed, as keys are matched directly to the ECU.
Hope this helps.
Cheers
Toni