Very little except have replaced the rear tyres about 20 times.
Whining rear diff my own fault, probably due to blasting it sideways out of roundabouts and hairpins.
The best car in the world, fantastic performance, handles like it's on rails, drifts like the wind and great, great fun. Hope to get the new M3 later next year.
Not the best car in the world, the best sports saloon in the world.