In the actuator (the mechanical assembly, mounted on the engine, that moves the throttle) there is a form of rheostat or potentiometer. It is used to feed back to the electronic amplifier (the one you just bought) throttle position information. If the potentiometer gets dirty or damaged, the position signal is lost and the system turns off. The dirty part is often in a speed area that the PO never used -- if your car was owned by someone who never went over 65 MPH, for example, you might expect the symptoms you're seeing.

If this is your problem, you may be able to fix it by taking the actuator apart and carefully cleaning the contact surfaces. There's a DIY somewhere -- did Diesel Giant do it, maybe?

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970