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