Veyron has multiple turbos, I don't think any one of them is "bigger" than the single turbo used in the 45 line of AMG cars. Well, they might be physically bigger(I don't know), but what I mean is that it provides the highest pressure(28psi) of any turbo used in a production car.

For comparison, Veyron has 4 turbos but they achieve "only" 18psi of boost( http://media.caranddriver.com/files/bugatti-veyron-164bugatt... )