A few weeks back I put TP on the gas analyser - idle CO% test was off scale high.
I knew this engine had done quite a lot of idling before being forgotten in the corner of a field for 20 odd years. As such I expected quite a bit of crud to be sitting in the inlet tract and the rings to be a bit sticky.
Nothing has changed here other than the engine having had a few miles of use at normal operating temperature. Reading speaks for itself really...she is definitely happier.