Okay, well, I had put this as one big jumble, but I figured if I broke it up into chunks, those who know more about one thing will be able to give input about something specific to each thread.
To start are the most important details: I have a 2002 WRX, No performance mods, had since Apr/May of '06 with 64,000 miles and I now have approx. 70,500 on the clock.
First off is my coil pack, or packs. The other day I changed my spark plugs. Everything went fine until the very end when I was putting the coil packs back on and I noticed that one of them had a broken tab where the clip for the wires goes. Because of this, they couldn't be secured tight onto the pack itself. My car had been idling extremely rough before, and while most of the plugs came out decent looking, that same plug with the broken coil pack (the upper right one if you're staring into the engine bay from the front of the car - what number cylinder would that be?) was pretty trashed. I had a sheet printed out of what certain things will do to a spark plug, but none of them really matched up, except, perhaps, of when you are running lean. And while I could have sworn that all the packs were fine before taking out the plugs and packs, I guess it's possible I just overlooked it the first time around. I made sure all the plugs were gapped - at .29 if I remember right - to the right proportions, and they were the right ones - NGK Iridium, platinum tipped, the right number but I can't recall it off the top of my head. I need to replace the bad pack, but should I also do the others as well? How tough of a job is it and how much $$ am I looking at? And how can I tell a coil pack is bad or is getting there?