Bad misfiring after exhaust work - undriveable

[Earendil]

What a saga! I just read through the entire thing :)

A couple thoughts. You've done great diagnostics on complicated issues, but maybe it's time to go back to basics. The engine needs Air, Fuel, and Spark.

Fuel:
I didn't see (or don't remember reading) where you say the fuel pressure is okay. A clogged fuel filter will cause these issues. On the more complicated side, I had an issue that (though not that bad) was caused by the wiring to the fuel pump. The ground wire was bad, but the fuel pump was still grounding (poorly) through the frame. This kept the fuel pump from keeping up, even though it sounded fine.

Air:
Take it to a shop and pay them $90 to do a smoke test at a time when you can watch them. A massive intake leak will cause a shitty idle.

It sounds like you are okay on spark, so let's tackle air and fuel first.

[RoDo]

Thanks to all for the ideas and feedback.

UPDATE:
It always turns out to something simple right? I took it to a local shop and it turned out to be the rotor. It was arcing and causing the misfire. I had removed the cap but not the rotor in my diagnostics. Cap looked fine and rotor looked fine without pulling it but that was it. I'm still kind of scratching my head as far as why the inside of the cap didn't show evidence of the arcing but the car is running great now.

So there you have it, another one for the files...