first off trash the K&N, you are asking for a future costly repair, why don't you clear the codes and switch the coils, besure to mark the ones that were originally misfiring and see if the misfire move with the coil, how is the engine wiring harness? after switching the coils try to get the codes pulled by a dealer or someone with a factory mercedes tool, if it is still doing the misfiring i would replace the crank sensor, but before you do disconnect it and see if there may be water or other liquid on the terminals. i have seen a few crank sensors cause this issue. if you do replace the crank sensor it is a good idea to reset the sensor gear adaptation, i believe the mercedes tool is the only way that is done