Back where the cables connect to the transmission, I wonder if we should also be looking at parts 15, 17, and 18 also (as referenced in the attached picture from the Porsche 986 parts listing), as it seems like they could potentially be sources of play, especially for left-right slop at the shift knob. I found an aftermarket replacement for part 17,
here.
(I also found some pictures of this overall contraption in jcslocum's post,
here. )