W124 w/M104 electronic throttle actuator wiring is TOAST!
 

I pulled the throttle body out of my 1993 300TE tonight and then disassembled it so I could examine the internal wiring.
The warnings about the condition of the pigtail harness were correct. The biodegradable wiring strikes again. It's weird though.
There are 11 different wires going from the external connector, traveling through a pigtail and connecting to a circuit board inside the unit and four of those wires seem to be just fine.
On those four wires the insulation is fine and the wires are flexible.
The other wires inside the harness are just 100% bare. No insulation at all.
Tomorrow I have to find a 9 volt battery so I can wires up some jumpers to test the internal clutch solenoid inside the unit.

https://i.imgur.com/q37tpBj.jpg
https://i.imgur.com/3l4mxLH.jpg

Is there still anyone that rebuilds these?

Victor from a youtube channel "vsandvs" he routinely rebuilds these units and makes videos for customers.

https://www.youtube.com/user/vsandvs

Also, You can try going to the bone yard and pick one up.

The ones in the boneyard will be as bad as the one you have. I rewired mine prophylactically a number of years ago during its off season.