Your dealer is sort of telling the truth(for a change).The concern is that the steering column's have been assembled with what Ford call a sub standard bearing fitted to the base of the column.Over time the bearing begins to litterally chew itself apart.Replacing the whole steering column is the only way to rectify this problem.I'm pretty sure that they arent going to recall any vehicles at this stage but they are releasing a TSB to cover this issue.Before anybody starts flaming me,I only supply the information so dont blame me. As for the steering shudder,seems strange that it only happens when you turn left.Can honestly say that I haven't come accross that.They either shudder all the time either way or they don't shudder at all.One thing you could try is to raise the vehicle so both front wheels are off the ground.Then turn the steering from lock to lock 40 times and see if that makes a difference.One thing to remember when doing this is to make sure the reservoir cap is "On",and dont undo it after this procedure either. Sorry I couldn't be more help FORDTECH