1.There are plastic bushings in the shifter linkages that wear out and need to be
replaced.Here's the Wicki for R+R:
http://www.peachparts.com/Wikka/W124ShiftBushings
1a What shape are your motor mounts in? What shape is your Transmission
Mount in ? 'Things "Bumping Around" down there can have weird effects.
2.Always solve "Power Making" problems with the engine before you try to adjust the "Bowden" shifter cable ( or the Vacuum Modulator)
3.Accelerator control Linkages and Rods must be adjusted to Specs BEFORE
any Tranny adjustments.
This is a great thread on Tranny Adjustments:
It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ...
AND STEVEBFL's :
http://www.peachparts.com/Wikka/TransVacTune
This is the Main Wicki for Mercedes Transmission:
Transmission: