just going to add to the confusion, i am sure.. but ...
many years ago - 89 GL wagon (EA82) started running like crap going down the highway - misfiring, etc, limped into a fuel station and found a cheap plug wire was arcing - also ended up with a bad O2 sensor on that car due to the misfiring. would stumble, misfire and run like crap even after putting good wires on - took it a long time to throw the code for the O2..
95 Legacy had random misfiring but usually on initial startup - would run like crap until warmed up.. after paying closer attention for a few days, it was always on damp days.. fog, rain, whatever... pop the hood and could actually see the arcing from the coil in full daylight when it was acting up. have a short video somewhere of it.