I have a 2003 m3 e46. Last year I replaced all the coils. A few weeks ago I replaced the thermostat and wsterpump. Its been running ok since. Today my CEL came on, red the codes and cylinder 3 is misfiring. When driving it will randomly stop misfiring and run perfectly fine, then go back to running poorly. I replaced the coil on that cylinder and same thing happens. Any ideas?