Nick,
Saturday, I did a lot of tire-swapping and rotating. Swap a couple, and drive, swap two more, drive, swap again, etc. When I started, the car was pulling slightly to the right, most of the time, and also some vibrating, but inconsistent. After various tire changes, the car is now pulling slightly to the left, and no vibration at all. So, I'm thinking that I must have a faulty tire somewhere. They're fairly new (less than 10 K), but I'm suspecting I've got a belt separation, or something like that. Just a thought...maybe it'll help you somewhat.
