I have a Quattroporte Sport GT 2007 with 65000 km on the clock. I only drive it during weekends in Cape Town and the car has never been in an accident or rough surface. Since October last year there have been vibrations in the steering wheel at speeds above 100km. This deteriorated over a period of time. All tyres where replaced, all rims where straightened and the propshaft was checked (and found to be ok). This helped a bit but the situation deteriorated again. Maserati convinced me to replace all rims with new ones at high expense - which I did - and whilst the situation has improved, I still feel vibrations through the steering wheel that I don't experience with other cars. Any further suggestions?