Hi again.
Today, I did two longer trips involving data logging and adaptation.
I didn't detect any connection breaks. The only change since the frustrating experience (constant error messages while the engine is running) was the new value for R 6, which is 3.3 kOhms.
With that, I moved a little further away from the Noxon values, and my part still runs better...
If I create an update to the circuit diagram now, other people might encounter problems with it.
For example, Gremlin is successfully using the Noxon-original circuit.
It's quite puzzling... I think I'll add a 10 kOhm trimmer in series with R6 (which is 1 kOhm). That way, the value of R6 can be varied between 1 and 11 kOhm.
Only then does the configuration of the part with already two trimmers (VR 1 and the new one) become increasingly complicated

.