You may also check into replacing spark plug wires and distributor cap.
I changed plugs on a vehicle and it did fine for a while, then it ran rough again, which led to changing distribtor cap and rotor button. White soot buildup caused intermitent conductivity. When it ran like crap again I took it to a shop who replaced the wires and all was good again.
It seems like I have been here for around 20 years or so...I used to be here every day, Several times. Then life get's busy, Times change, Priorities change etc...I always have checked in and had a look around. This is truly a Great Forum. Calm, Cool and Collect 🙂 I'll never not come here for information.