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Yea, get your wheels balanced and you should be able to take it well past 200, when you hit around 180-200 you'll find your vehicle should get a LOT more responsive, handles better and grips better.
andyman, i'm not saying to do that on a public road, but if you do take a VY or VZ (Supercharged 6 or SS) up at those speeds they become more responsive. Maybe the rear spoiler that was on the vehicles might've done a little bit too to lower the rear ends at those speeds?