This 2006 BMW M6 V10 came in rough running with a misfire. The misfire was easily located and diagnosed, but trouble arose when the coil at cylinder 10 broke. The top electrical connector portion snapped off when the mechanic was attempting to remove it from the engine.
This tech note is more about how to I got the coil out verse the usual diagnostic study.
The tech attempted to extract the coil using needle nose hose pliers, but it would not budge. The rubber boot was stuck to the spark plug and it was slowly falling apart with each attempt at removal.
To remove the coil, we drilled a hole in the center of the coil top.
Then we screwed in a 3 mm sheet metal screw with a washer.
Next, using the nub on the valve cover, we levered the coil out using a prybar. Now be careful when you get to this point. The coil is brittle and you will only get one shot at it.
You can see here how dry the boot was and the brown residue inside inside.
Be sure when installing the new coil to apply a small amount of dielectric grease to the boot to prevent this from happening in the future.