Yep, on the E60, it needs vacuum to keep the exhaust flap open. In the case of the 550i, that flap when open full-time results into a nice GROWL on startup and a very sexy Burrrble on idle. Other than that, acceleration or cruise speed sounds the same in the cockpit.
2007 550i, Sport Premium, Silver Gray Metallic, Gray Dakota, Navigation, Cold Weather Package, Comfort Access, Heated Rear Seats, HD Radio, Xenon
2007 X3, 3.0si ///M
Sport Premium, Monaco Blue, Gray Dakota, Navigation, Cold Weather Package, Xenon
2002 X5, 3.0i Sport Premium, Titanium Silver, Gray Dakota, Cold Weather Package, Xenon, just a winter vehicle