I have never heard of an EGR causing a misfire code. When you changed the spark plugs, did you change the coil? I would bet that the coil is failing. What you need to do is get a spark strength tester and check the sparks coming from the coil to the spark plug.
With the engine off, you will unplug cylinder four's plug wire, and connect the tester to the spark plug on one end and the wire on the other end. Start the car and observe the spark. Turn off the car, and run the test on a cylinder that is not having a misfire code, like number one. Compare the spark color and frequency. Blue sparks are stronger than yellow sparks.
This is the spark tester that I use: https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6/ref=sr_1_3?ie=UTF8&qid=1497320343&sr=8-3&keywords=spark+tester
Monday, June 12th, 2017 AT 7:21 PM