Steering retrofit problems on 2001 330i

I had the steering retrofit done on my 2001 330i last year and while the steering now has a better return to center on turns, there is a loose-feeling dead spot in the center of the steering. This causes the driver to feel the road a lot more than before the retrofit, but in a negative way. While the retrofit was supposed to make my car's steering heavier, my steering still feels overboosted in the the center and it's difficult to steer the car straight without feeling every imperfection in the road and having to constantly correct the steering wheel. I brought my car back in to the dealer and had them do a 2nd alignment thinking that this would fix the problem. While it initially made the steering heavier, within two weeks the steering has become overboosted again. After checking it out, the dealer claims that the alignment specs have not changed at all since they did the 2nd alignment.

Has anyone here had a similar experience with their steering after having done the retrofit? If so, how did you get the problem corrected?

I don't know if the retrofit steering rack or the alignment jobs that have been done are the culprit. Two other 330s that were retrofitted that I've driven have heavier steering with much more resistance in the center of their steering.