Sooo... I went back to the dealer and drove both my car and the other ST. Mine still had the vibration but the other ST did not. So I asked them to swap the wheels again so I could drive my car with the other ST's wheels and tires. No vibration in my car at that time. So they let me keep the wheels and tires from the other new ST. Drove home (about 50 miles) with no vibrations! Sweet... but...
Now I have a tire pressure sensor error/warning popping up on the message console on the gauge cluster! Ugh...Wonder if they didn't attach something or if something got disconnected/broken when they were swapping wheels back and forth between the two cars? I'll have to call them about that on Monday. At least my vibration is gone now.