hey :) i just bought the same car as you not so long ago. umm i havent experienced any bad vibrations when travelling at speed. what i have noticed were noises comming from the tyres the first few weeks. they have those little rubber tenticle thingies :| duno how else to describe the lil bastardS!!!! and i also found that HEAPS of rocks got caught in the tyres which made all sorts of horrible noises
i suggest taking it to bob jane or one of the more respected tyre fitting companies as they usualy have better technology and service. also find what side the vibration is comming from and if its from the back or front and get your shocks and springs checked out by a suspension place. thats all i can think of.. good luck. let us know if u find out what the problem was