Here is a track-driving Video:
Translation:
The driver first is saying that the interior is still not finished and that the press-man should not give it to much attention. Then the press-man says that the car goes really much better than the 135i and that it must have a powerful engine at about 350PS (345HP) as it is an M. Then the driver says that this car is more about handling than only HP.. but he was then saying that it has much power as it is expected from M but he will not reveal any specs right now. The press-man also noticed that the car handles really good and he said that he can feel that it is much lighter than the 135i.