Could you give me a little history on the car? How long have you had the car? How long have you had the running rich problem? Does it run rich when cold, warm, or both? What kind of plugs did you put in the car?
The low vacuum could be because of the #8 cly problem and/or a vacuum leak.
I don't think the Euro cars had an ECU. There is a 2 terminal coolant sensor in either the left or right rear of the engine but it disables the heater fan until coolant gets to 120(?) deg f. Even if it had an ECU it wouldn't have a temp sensor. The warm up mixture is done by the Warm up compensator or sometimes called a control pressure regulator. It is a small box about 2X3 with 2 fuel lines and 2 wires and maybe 1 or 2 vacuum lines. It is at the left front side of the engine looking at the engine from the front of the car.

Paul

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84 500 SEL (307,xxx miles)