Posting here as this thread was very helpful for me.
My 2009 E92 M3 (90k miles) went into limp mode a couple of weeks ago. Threw several misfire codes among them being P138C (cylinder 8 misfire). I went in and replaced the spark plug with an NGK plug and the ignition coil with one from Autozone (before I found this thread). Car would drive fine until warm (10ish minutes) and then go into limp mode. Pulled the coil and plug again and found fuel on the plug. Thought it may be the dreaded injector failure and so I scoped the cylinder, ran compression (came back at 180psi) and replaced the injector… same issue… 10 minutes into driving, limp mode and P138C. Found this thread and immediately ordered OEM ignition coil from FCP. Just installed it and have been driving the car with no issues.