I took my 961 for a slow run using between 1500 and 2500 RPM. The engine is quite uncomfortable at those RPM. I ran for about 30 minutes on twisties. At the end of the run, I turned the engine straight off and didn't let it idle at all. I wanted to see what the fueling was like in this rev range. I removed a spark plug to find it very black and sooty. It has NGK iridium spark plugs.
Now, the 961 is fuel injected so mixture is out of user control. The question I have is "does anyone know of a reason for the ECU to get the mixture so very wrong"?