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.

Is there still anyone that rebuilds these?

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

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.

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200 75 W115 (Mom's)
190e 90 2.6 W201
E320 95 Wagon W124
72 BMW 3.0 CSI

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.

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95 E320 Cabriolet, 159K