There are a few cars which go through a lot of modifications and performance upgrades. The aftermarket firms spend a lot of time and go to great lengths to create a bespoke body parts to these most exclusive cars in the world.
The Mansory is a perfect example for this. But, this is definitely not required to the Bugatti Veyron. Recently, in one of the Sporting Charity event in Hungary, a Grand Sport Vitesse WRC with a Mansory exhaust was seen beside a Veyron.
This was one of the most understated upgrade, because the exhaust makes a hell of a noise, when the 8.0 Liter quad Turbo, starts to get going.