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The past few days my 2013 Edge with 102,000 on it, has been running rough and today the check engine light came on. The code was P0304 which is #4 cylinder misfire. Will replacing the plug and coil fix the problem?

I have been having an issue with my 2011 Edge running rough at idle. The edge has 77,000 miles. Here's the story: I was having trouble with a cylinder misfire under normal driving. The code read "misfire cylinder 5". I took it into the dealer. They told me I had a bad coil on cylinder 2. They would replace it for $800, but recommended replacing all of them for $2,500. I passed on their offer and performed the repair myself. I found a cracked insulator on the spark plug at cylinder 5. I replaced all of the coils and spark plugs anyways - for good measure. The misfiring cylinder was solved. Since I was under the hood and had the intake off, I took the opportunity to swap out my air filter and clean the mass airflow sensor. I bought a nice K&N air filter and installed it and cleaned the mass airflow sensor with CRC mass airflow sensor cleaner. After driving around for a while, I got a check engine light with fuel/air codes. I figured this was due to the increased airflow from the new high-performance filter. I swapped it out for a normal paper filter. The engine codes went away. Well, it seems these things come in threes: The following few weeks, the engine started running very rough at idle. I suspected a vacuum leak somewhere. I removed the intake manifold, to see if I had damaged a gasket , or forgot to connect a line. Everything looked good. Then, I checked the Emissions Vapor Canister Purge Valve and it does not appear to be malfunctioning. All the lines on the intake side appear to be seated correctly. Does anyone have any suggestions on where to look next? -Thank you in advance