Hmm... It's been ages since I've looked, and my memory isn't so good, but I could swear the 123 steering wheel was placed on a six sided hex shaft rather than a splined shaft. Hence the granularity of adjustment would be 60 degrees - hardly fine enough for this kind of detail work.

As well, the car will drive better with the steering box on center in the straight ahead position. The box has reduced play at straight ahead, presumably for better control. Off center it has more play, for reduced friction, I think. If the steering wheel has been changed, driving straight down the road means having the steering box off center - in the area where it has increased play. Check out the manual section on adjusting the steering gearbox freeplay - it has a graph showing the torque required to move the wheel at each point from lock to lock. The required effort is lower on the ends and highest in the middle.