I think the mystery of the 123 steering box is a sort of sick joke. It has to be a joke that they ended up with something so bad in an otherwise masterpiece of an automobile.

There are several pro tech's who frequent this site who say that you should not touch the adjustment, period.

That said there have been a number of people mess with these boxes. I see very few 123's with a tight box, but I've never been able to tighten one up satisfactorily.

About the best I've been able to do is; hold the allen screw firmly in it's position and loosen the nut completely with maybe a half turn of the nut, then turn the allen screw counterclockwise ever so slowly until you feel the slightest resistance. Then, hold the allen in that position while tightening the nut. You may have to tighten the nut several times to get the allen in that spot after the locknut is tightened.

Also, raise the front of the car and check the tie rod ends and idler arm for slack.

I hope this helps.