P code is misfire on number four fuel injector

The symptoms of the problem are: The car will run fine then at low speed and RPM's it will begin to chug slightly. The chugging continues and increases after about thirty seconds and continues to grow more severe until service engine light comes on steady, then intermittently becomes a flashing service engine light.

I pull over inside engine down for about five minutes. Perhaps slightly more. Then, when I restart the engine it seems to run alright.

My plan is to replace the fuel injector on number four. My question is, would it be beneficial and cost-effective to replace all the fuel injectors and the spark plugs once I get the upper intake manifold off anyway? If I have it that wide open why not just do the other things? One possible why not is if it is not necessary do not mess with it.

One last thing, I had a problem similar to this about three years ago with the same car and I even believe the same cylinder but I am not sure. After struggling for weeks to figure out what the problem was and fixing and figuring out what the problem was and fixing. I finally figured out that it was the ECM. Does it sound like there is any chance that the ECM could go out yet again on the same car? Is this a known problem?

Thanks for your help.