Cylinder 4 misfire, or is it?

[D1n60]

Car: 2003 9-3 ARC

I've had this nagging issue for about a month now. The first symptom was that the car would hesitate under heavy acceleration. I though it was the boost control valve because it would only happen when the turbo was spooled all the way up. So first I tried to blow it out hoping it was blocked. It seemed to work so I left it alone. A week later after a long drive the stutter came back but I had to take the car get some repair work after someone hit me. So today after i picked it up I went to put my foot down to see what was going on and I got a flashing CEL. After driving it around some more the CEL stayed on and gave me a P0304 Cylinder 4 misfire. Before I took the car in to the shop I had replaced all the spark plugs so I decided to swap the 3 and 4 ignition coil. Now the car doesn't stutter however after doing some research it seems that a blinking CEL is caused by an overheating catalytic converter. The overheating catalytic converter could be caused by a misfire from what I have been told. This one is complicated, I have an appointment with my Saab dealership to get it looked at but if I can figure it out before then I would be much happier.

So here is the break down, car hesitates under heavy acceleration once the catalytic converter is hot. This seems to be the main symptom. I got a P0304 Cylinder 4 misfire but I can not reproduce it after swapping my ignition coils. Also my current MPG is about 21 which is low in my opinion and from what I have seen other people get. So any help would be appreciated because I would rather fix my own car then have the dealer do it.

[Burnsside42]

New coil pack and fresh proper spark plugs and away you go.