You do not have to pull the bumper off to install the fog lights. There are steel brackets held on by 6 or 7 15mm bolts and you also have to remove the bumper support bracket.
Why not swap #8 coil to #6 cylinder and see if the misfire follows? If it does you have a bad coil. If it doesn't you probably have a bad injector. I'm leaning towards the injector personally though.