http://www.autocar.co.uk/car-review/bmw/m5/first-drives/bmw-m5-competition-package-first-drive-review
http://www.autocar.co.uk/car-review/bmw/m5/first-drives/bmw-m5-competition-package-first-drive-review
Actually good value when you brake it all down.
A standard (non-carbon) BBK kit would set you back a few grand for a car like that and then an set of rear silencers would probably set you back another 2-3 grand.
So you're basically getting and engine map, suspension upgrade, diff and traction settings for free.