The O2 sensor may be bad, however, your plugs should not look like that. I have seen thousands of plugs (most of them from my over-modded Talon) and they should all have the same (roughly) amount of carbon on them. For my Talon, Cylinder one has the most amount of carbon and cylinder 4 has the least but it is a smooth progression and they look roughly the same. Your engine is obviously different, but the same rules apply.
Tell me if I am correct with this: The plug with the most carbon is the one cylinder that has no misfires.
If you have a friend with wideband (high quality, high accuracy AFR meter) have them do some datalogging with it. Also, as I said earlier, some data logs from the ECU would be invaluable.
Originally Posted by canis
Dealer still has my car. After speaking with the tech line, they say it's the pre-cat air/fuel ratio sensor (O2 sensor), which they've ordered. If the car had a bad O2 sensor, isn't the computer sophisticated enough to say "you have a bad O2 sensor?"