The mixture didn't burn in #1 cylinder. All that unburned O2 mixes with the other cylinders making the overall mixture look lean.
The raw unburned gasoline has no O2, the vapor has some O2. Whatever amount of air (mostly nitrogen) that was being pumped into exhaust manifold from number 1 cylinder was NOT enough to make the mixture look lean to the O2 sensor.
The spark plugs were not getting a rich mixture. Please explain what the O2 sensor was seeing?
BUT.. that is history... I need to know why the chambers, based upon my thinking that the spark plugs look like they are seeing a lean mixture, are getting a lean mixture?
Thanks,
Gnarls.