u should take it to a different shop to get balanced man...
about 2 years back i had my winter tires switched on the spec rims to newer winter tires and after that happened and i took her for a rip...it shook after 100km/h...i brought it back to the shop and they said that my rims are dented...
i asked them why didn't the old setup do that and they didn't really have an answer except for the fact that the other tires were better...they were "only" dunlops and they were BOLD! lol
so i asked them to rebalance them which they refused, instaed they just put one of the wheels on the balancing maching and without even properly securing them showed me that my rims were SLIGHTLY dented...at that point i just gave up on them...
around that time my buddies at
Exclusive Wheel and Tire just opened their shop so i took my new tires/rims there...sure enough they managed to get them balanced PROPERLY not like the lazy f*ck at 2nd Time Around in Oshawa and off i was happy as ever

not saying that's your problem but it has happened to me so i thought i'd share

and if you haven't figured out your problem by the time u come back to the toronto area, visit John and Keith at Exclusive Wheel and Tire