I have had this happen twice. Mine was cylinder 6 misfire, along with multiple cylinder misfire. The first time it happened I changed the plugs. The second time I did nothing, other than erase the codes with the OBDII. The weird thing is that both times this happened I had the air filter (K&N) and assembly off (at the upper intake) of the vehicle a few hours prior to it throwing the misfire. It also happened after passing a vehicle (yes this can happen) and letting off the accelerator quickly. Haven't quite figured it out, but it hasn't happened since, and I haven't had my air filter out since. I have also ran Sea Foam through the intake, crankcase (about 100 miles before last oil change), and gas tank, and Marvel Mystery Oil in the oil just as a precaution.