IOW O2 sensors are not fast enough? (Just as I thought.)
So are they fast enough to react to a single cycle (2 crank rotations)? Not that I think they can be mounted in each header, and I suspect with a newish engine (4 valves per cyl etc) you would not want long headers...(??)
The only method I know for what you want is ionic. O2 sensors just don't cut it - tho I may be out of date re O2 sensor technology (not that afaik the basics have changed - ergo, still useless).