Note, if you have misfire, the O2 sensor numbers will be bogus to a degree. Bogus O2 numbers will mess up the computer's feed to the other cylinders as it cannot know they are functional, and don't need extra fuel to eat up the excessive O2's found(due to not being used up because of misfire).
Fixing the misfire before trying to diagnose fuel trims would be my method of attacking the problem.
I would do a compression test, and/or check the ignition system for failing bits. Measure the ohms of the plug wires, for example. If they are 'open' the spark voltage needed to fire the plug will be increased as the voltage must also jump gaps in the wire...
tom