I finally got my car running well again. Then met up with some OPPOS for a canyon drive. I did about 125 miles that day and the car never missed a beat.
I tracked down the misfire to no spark on cylinder 6 and 7. I changed the coil pack on that side (cylinders 5-8), the igniters, checked the wires, and changed the spark plugs to no avail. After looking a little deeper, I realized 6/7 were (eventually) driven off the same wire from the ecu. So I checked continuity in the harness and pull the ecu. I am greeted by this lovely corrosion:
From there, I clean off the pins with a combination of contact cleaner, brushes, sand paper, and swearing. I hit it with some air duster and threw the ecu back in the car. The car fired right up and ran well. From there I changed the oil because I was worried about fuel dilution. After a quick shakedown run late Friday night, I parked her in the garage, ready for the oppo meet. I dug pretty deep into the car and learned a lot. I’m glad I was stubborn enough to keep tracing the problem, even though it was out of my expertise. It feels good to actually fix something.
Shot out to TFritch to answering my questions along the way.