you absolutely do.
the fact that they misjudged the wastegate, vane angles etc (whetver they did), IS THEIR PROBLEM. can you prove that the car is a dog though ??
in the u.s. ford cheated on horsepower figures on mustangs (they since owned up and are offering a retrofit at their cost), and mazda similarly on the miata (mx-5 where you live i guess). so there is precedent....
you bought a car that you test drove. write to munich, and threaten a law suit. in the u.s, if you d'found enough pissed owners this would qualify for a class-action ( i.e. try to prove that bmw cheated a bunch of angry people), i have no clue what is available in s.a.
i am sorry that this advice is so lame, but usually it just takes huge patience to deal with stuff like this...
next time buy the 330d. pavement pealing torque.