Some speed rated tires /directional will have a roar at speed.Are you sure its a vibration or just tire noise.If there was a mechanical problem especially in the front tires or suspension you would feel the vibration transmit to the steering wheel causing a vibration or even a jerking motion.I would say I the problem was not present before you changed tires then the tires are the culprit. I know the tires on my car are very noisy at speed compared to a touring tire.That's just the characteristics of some tires out there. How ever I would not think so of the Pilot sports. They are a very good tire.
Tim