Hi, CO at idle approx. 8%, scoping O2 sensor at sensor showed flat line at 900mV and pulling off vac line to allow air in resulted in very minor signal change and sensor is very sluggish in its response, if any.
Using EOBD the O2 signal from ECU showed approx. 350mV constant.
Removed the O2 sensor to inspect and it was choked with soot, as expected really.
New sensor fitted - same result. I have checked signal wire back to ECU multiplug and have 0.1 ohms.
Next I scoped signal at sensor and signal at ECU multiplug and they were identical but the EOBD value was 350mV.
Am I looking at a faulty ECU here or have I missed something more obvious?

Thanks for your time, Martin.