Sergio - welcome to the world of FI! In boosted motors the 100 octane does more good than it did in your e46. Turbo motors generate a ton more heat and are more likely to detonate. So regardless of whether the car is tuned or not, I always run as much 100 as possible during our schools. It is critical to keep these motors away from the threshold of detonation during prolonged WOT sessions. The 100 doesn't add power, it simply helps keep the motor happy and safe.
When you drove my car it was about 2/3 100, 1/3 91.
2010 Evo X - track/kiddie carpool beast [sold]
2013 328i - Wife's Car
2012 328i ED (June 12)