One of the hardest codes to track down.
The system has detected a misfire that cannot be attributed to any one cylinder.
The best way to go is cheapest first, so install new, properly gapped spark plugs and replace the plug wires. That will leave only the much more expensive coils and ignition control module for that system.
If no change then move on to the fuel system before spending big bucks.
also this could be caused by bad fuel performance or clogged injectors so change the fuel filter, check fuel pump performance, and first try a fuel injector cleaner before removing and cleaning them or replacing them.
O2 sensors are relatively cheap and could possibly set off the code.
If all this fails ( basicly what you have done is a tune up) I suggest having the car put on an engine diagnostic computer to possibly track down the source of the misfire.
Changing out any of the more expensive parts without knowing if it will repair the problem is not a good idea and is costly, an engine diagnostic will cost around $100 and is well worth the money when the tune up has not improved the situation.