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.
Obligatory:
Shot out to TFritch to answering my questions along the way.