P0302 CEL - advise/help/expereices

[saab90089]

I have had a CEL (P0302-misfire cyc. 2) for a month or 2 now. I can not seem to figure out what is causing the CEL. I would like some advise from anyone as to what may be causing it or how to get rid of it.

Car Information:
1997 Impreza L
2.2ltr N/A
5speed
250K miles

What I have tried so far:
-Replace plugs
-replace wires
-replace coil-pack (when this did not solve the problem I returned the new part)
-replaced ignition module (located on firewall behind airbox - also swapped back when this did not solve problem)
-Replaced cyc. 2 fuel injector

As I stated before none of the above solutions have solved the problem. I feel that I have elminated most of the obvious stuff. I have a few ideas that I will list below, tell me what you think...

Ideas I think may solve the problem:
-replace plugs again: perhaps the problem is solved but plug is fouled?
-replace coolant temperature sensor: I've read here/there this might be the problem?
-Valve Adjustment: to my knowledge the valves have never been adjusted and I wonder if at 250K they could be off enough to cause this? I have also read this was the solution for someone else.

If anyone has any other ideas or suggestions or theories please post.

Thanks,
Ian