The electrician checked all the available values, no problem.
But, I remember that the car had been in a garage for a precautionary belts change, and therefore they have to remove the boost hoses, so I checked them and the intercooler to throttle housing one had a leak... I fitted it better and now, at least when warm, no more hunting, 950 rpm idle...
I'll check this evening with a cold start.
Cheers.