Very strange, you have no Engine Management light or flashing Traction Control symbol. But still have a misfire? The EM system monitors all parameters and should register the fault even if mechanical as the engine would expel un-burnt fuel.
It would be strange but not impossible for all the coil packs to fail at once, whilst a certain fault code points to a potential problem area it does not always mean the specific item is at fault. I might look at the crankshaft & camshaft sensors as these do the job of an old fashion distributor, if it is giving false data to the ECU the engine may misfire? But again this would be picked up by the EM system.
Is the misfire right across the rev range?
Do you have the original fault code as that may help.