Considering these motors are positive displacement supercharged so they pull air through the throttle one can see how this is a significant point of restriction. For W211 E55's in particular the throttle body upgrade is a good place to pick up power. This upgrade and its benefits applies as an option only for those who get the Weistec supercharger upgrade.
Expect gains of 20-50 horsepower depending on the setup, supporting mods, etc. In this specific example the 82mm throttle body is good for about another 28 wheel horsepower on the factory 74mm with the Weistec supercharger upgrade:
For more details and to order: http://www.weistec.com/m113k82tb.html