2000 Toyota Tacoma rough idle

I recently retrieved data from the cars computer because the check engine light was on. I purchased the carmd scan tool to do this. From the code retrieval carmd said the most likely problem was a malfuntion with the number 2 cylinder ignition coil.I replaced the ignition coil and the check engine light went out. It seemed to be running better but I noticed the car was idling rough. Then about a week later the check engine light came back on.What kind of things can you do to smooth out the idle.Thanks conrad.