C280. Vibration.

Hi all...

I recently purchased a 1994 C280.
The vehicle has Intra 17" wheels with some taiwanese tyres (Nankang).
There is a vibration on the steering wheel even at lower speeds (eg. 60Kmh) and I notice the vibration can be felt from the seat as well.
Mercedes Service said it is because the lower control arm bushes are worn but the place that I bought the vehicle from doesn't believe so and has attempted to fix the problem yet I feel the vibration is still existent.

Any idea who is right?

Thanks
alex