[CWizard]

I've read several posts here about various front wheel shake problems, but none of them seem to match this. My new Superformance has a pronounced front wheel shake that starts at about 70 mph and lasts to about 80. The steering column is actually moving, not just the steering wheel. All of the vibration seems to be coming from the front (for example, my butt isn't shaking), so I'm pretty sure it's a front end issue. Had this problem from day 1. So far, the dealer has replaced both front wheels and tires, and rebalanced the new front tires. Still shakin. Could a front wheel alignment problem cause this? Could the rear wheels cause this? Help!
And thanks very much.