I have a stock 2000 impreza 2.2l. In the beginning, if it was damp/raining, the car would miss and the CEL would flash for the 1st minute or less of driving. Then, it would smooth out and be fine. Well, this started getting worse until the CEL stayed on and the engine wouldn't stop missing. I checked the code and it pulled a p0304 misfire on cylinder #4 error. I tried new plugs and wires but no luck. I swapped the #2 & #4 injectors and reset the code. After about 2 miles of driving, the p0304 came back. I looked at the new plugs on the left side and #2 looked like new but #4 was already blackened. I am going to check the compression on #2 and #4 to see if there is much of a difference. However, the way it was acting in the beginning seems more electrical than mechanical. The coil on this car is a single unit. I can see no cracks anwhere in the case on it. Any suggestions on what else to look at? Thanks!