I can tell you it's not the alignment. I have the worst alignment know to man and I have absolutely not a twitch in the steering wheel past or under 90. Did you try to re-torque your wheels? Loosen them and re-do the lugs in a correct fashion to the proper torque specs. How many miles on your tires? You said they were balanced 10 times, but are they new are 50,000 mile old? Maybe some suspension componant is worn or lose. If all these suggestions fail check in with a mechanic to check the parts on your suspension. CV joint, endlinks, who knows. Good luck.