Well, if you did notice a miss on the two suspect cylinders with a timing light, then something in the ignition system should be suspected.
Right but the timing light won't light if the spark plug does not actually spark due to fouling (to complete the circuit), and the ignition system could be fine. That is why I swapped the bad plug to another cylinder to see if the problem moved with the plug and it did, which indicated the ignition system is ok.
