Well, it seems like the dealer couldn't figure out the problem yet. They swapped coils and injectors to see if the miss occurs on the same of diff cylinder, but after that they couldn't get to fail again, so now I have to pick it up again... I doubt it's been fixed...
It's a dramatic hessitation for a split second, so it's obvious even to passengers. Only happens on hard acceleration above 3K RPM.
I don't think this is an X1 thing, I think it's the N20 or the 8-spd tranny.
I'll keep you posted on what I find out tomorrow.