e28 525e

Possibly Dr. Dieter Waldman, although the article I have from their ~2002 magazine says he mostly worked on 7 & 8 series.

However a quick Google reveals: -

Claus Luthe, (December 8, 1932 - March 17, 2008)

Luthe, then, was tasked with developing a facelift for the aging E12

5-series within a budget of USD 100 million.[9] Luthe solved the cost restraint problem by reusing the passenger compartment structure of the E12, but with new front and rear clips and a new interior. Significant technical developments, such as new front and rear axles as well as climate control, were also added, and eventually the project cost for the new model, the E28 reached USD 400 million. However, the BMW management was satisfied that the improvements in the E28 were well worth the costs.

He left BMW in 1990 after stabbing his son to death.