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I'm no expert but I had this similiar problem. Except there was oil on the coilpack because of the rubber seal was torn and was causing oil to get in the coilpack. So it cause one of the coilpacks to go bad. So it basicly was running on 3 cylinders with check engine light flashing. It sounded like a harley with my loud exhaust. Very rough idle and accel up from 1k to 4k. It seemed to smooth out some at higher rpms but not as bad.
What you can do is pull the wires from the coilpack starting from the front to the back as the car is on. When you notice a difference in idle then you know one of them are bad but only pull it for like a half a second and if you notice a change then push it back in immediately. If it changes then you know that one isn't the bad one.