I had a similar high speed vibration that appeared at 180 kph all the way through to 225 kph, which was cured with a dynamic wheel balance of the front wheels done at the dealer here in Edmonton.
They have the equipment to spin the wheels on the vehicle and balance them "dynamically" instead of the usual static, or wheels-off balance. This procedure also balances any vibration in the other rotational components attached to the wheels such as the brake disks.
The service manager said they had to get that equipment a few years ago when the S-class was having problems with faulty wheels, so I'd assume they would have it in Calgary too.
It worked wonders...now I need to improve the aerodynamics a bit 'cause she begins to float a little when driving above 220 kph!