I thought I'd post the attached, which is an email Lee kindly provided me with that describes the adjustment of the Bowden cable. Good luck....wish I could offer a solution.

"...You want to pull the car out where you have reasonably good lighting.
Then open the hood all the way. (vertical) Look dead center behind the
engine, between the back of the airbox and the firewall. You will see a
cable and beneath the cable, a bolt with two rounded socket ends. The bolt
is what you will be adjusting. Before we take that out look towards the
driver's side past the cable/double ended bolt. You will see two black
plastic pointers with red painted ends. When the Bowden cable is at "spec"
those two red lines/arrows should line up perfectly. By lengthening the
double-ended bolt you raise the shift points and firmness. By shortening
the bolt you slur shifts and lower shift points. Hence, when the arrow
closest to the front of the car is closer to the driver's side fender it is
"more aggressive" adjustment. When the front arrow is closer to the
passenger side fender (than the stationary arrow that is closer to the
firewall) it is "less aggressive" adjustment. I find it easier to brake one
end of the bolt loose from its mounting point and turn the bolt while the
other end is still attached. This may not always work, but it makes "fine
tuning" much easier because you know you are only "1 turn past spec" or
whatever.
To get the bolt off of its points: Spray some WD40 or something on the
bolt as it may be a touch stiff. Then insert a flathead screwdriver between
the mounting point "ball" and the "socket" at the end of the bolt. Twist
the screwdriver to pry it apart/loose. It may not go all the way off, but
you should get it mostly loose. A good jerk by hand or tap with something
mildly heavy (1-3 lbs) should take it the rest of the way. If you can now
adjust length. If you want to take the bolt completely off just repeat
above steps for the other side. BE CAREFUL, if that bolt falls down into
the engine bay you are really in the ****. To put the bolt back on just
place the open end of the bolt over a mounting point and pinch it on with
your fingers, it should snap right on. (be damn sure to wear insulating
gloves through this) If you need help twisting any of the nuts on the bolt
you can use the small wrench in the OEM toolkit. (8mm I believe)
Adjusting length should be a snap once you brake it loose and get a good
look at it. Longer bolt = more aggressive shifting. Shorter bolt = less
aggressive shifting. Keep an eye on the arrows for reference. I like it
about one full "revolution" (that term will make sense once you get it out
mess with it) past "spec". You can tune it to your preferences. For quick
reference: break loose, adjust to spec, put back on, take one end off its
mounting point, then adjust the bolt one "revolution" at a time until you
find a setting you like..."


------------------
Best regards, Michael
'92 500E
'88 300TE