thrumming felt in 300E steering wheel between 85 and 95 KPHs

After installation of a donut shaped isolator around the driveshaft(layman's terms), the car now exhibits a pulsing sort of thrumming feel between 85 and 95 KPH. It is not noticeable below this speed or above 100Kph. It has been suggested that this isolator is too tight. It is ostensibly there to prevent a tendency to clunk when Drive or Reverse is engaged, from a rest position. The wheels and tires are fine and the car is otherwise great. Low mileage of 115,000KMs. The suspension and front end has been fully updated and serviced.
It was not there before this 'donut' isolator was replaced. Any ideas?

al