Strongly urge using a regular gas extender engine. Premium gas is/will always be/ about $0.20-$0.25 per gallon more expensive. Most supercharged engines demand it.

It would really be cool if they did have a turbocharger and controlled it's waste gate electronically. That way when you're running E85 you could activate it and gain the efficiency. e85 has a very high octane rating. When you use regular gas just leave the wastegate open so the exhaust gasses simply bypass the turbo.