I've been having a misfire in my 3rd cylinder since December.

I originally switched the spark plugs and it was fine for 2-3 weeks. Got the code again

parked it, couple weeks later switch spark plug again drive around its fine next morning get the code. Switch the spark plug cables on cylinders 1 & 3, same story drive around all night and in the morning the codes back.

2 weeks ago I swapped ignition coils on Cylinder 3 &4, drove for a week and a half and now I keep getting the code.

I'm at a loss of what it could be, the rpm's have been a bit higher than normal. But I just need ideas. I am going to try swapping the fuel injectors, but want to know if something similar has happened to anyone else? If so what did you do?