Graham,
Thanks for the info!

Today I installed the 'new' ECU, idled the car until it was up to temp. The idle mixture plug was set all the way CCW (lean). Once the engine cooled down I pulled a plug and it was black, ie still rich.
I checked the coolant temp sensor resistance at the ECU with the engine at ~180F and it was just 395 ohms. It was 380 at the sensor. I have not checked the graph, but that sounds to be in range. I will also check the air temp sensor tomorrow.
bye,

Csaba