Have you tried contacting your parents' insurance company? You should be able to get a multi-vehicle discount (and a lines of business discount if they have their home and auto insured at one place). If your quote was from the same place, confirm that all the discounts are in place.
The car you drive isn't going to make much of a difference at this point. If anything the E92 is a pretty good car for insurance. Your age, location and driving history have the biggest impact. And as Zebra said, some insurance companies are just more expensive than others.
Wide open road, wide open throttle.