Mystery vibration 2010 Ford Focus?

Ok. I bought a new 2010 Ford Focus SEL in July. It's fully loaded w/leather, sync, etc....I have a long commute so I have racked up the miles fast. I'm now at 7300 miles. The day I bought the car I had some vibration, but I didn't think much of it due to being on the lot for a while. I figured there were flat spots on the tires or whatever. A couple weeks later I took it to my local small-town Ford dealer who balanced the tires. I was also told, "we didn't get the problem fixed because this dealership doesn't have a road force balance tester and Ford requires that to warranty your tires." I was a little miffed, but took it over 50 miles back to the dealership where I bought it. I don't want to name the dealerships yet, but this one is a large dealership in Indianapolis. They "re-indexed" the tires on the road force balance machine and said "we got 95% of the vibration out and it will get better the longer you drive it. Sre enough, the was bogus. I put up with it a couple more months and took it back to that dealership a week ago. They "re-indexed" my tires again and told me that each tire was well within Ford's specs on the road force balance tester. I drove home sick to my stomach because it still vibrated. Today I brought it back and took the service manager on a drive. I actually had him drive while I rode along. He did notice the vibration which varies in intensity as you drive within 65-80 MPH leading him to believe it is not the tires. They special ordered some specialized equipment to diagnose it today. Dealership claims it cost them over $2300 for the equipment, but I wasn't the only customer experiencing this. Thanks for reading through the long explanation. Any ideas what the hell is wrong with this thing?