Finally installed the Soul Performance Competition Headers I bought from another owner and updated to the Cobb Stage 2 93 Octane tune. While I had the exhaust manifolds out, I went ahead and replaced all 6 coil packs and plugs since access was unrestricted.
When I first fired it up, it was running horribly and throwing tons of codes. Threw the code reader on it and found misfires on cylinders 1 and 2. Pulled that tire to check things out and it turned out that I'd not quite reconnected those coilpacks all the way. Each was only maybe 1/16" from fully plugged in, but that was enough to cause problems. Pushed those all together fully, cleared the codes, and it started and ran smoothly. Just to be safe running the catless headers, I did use the Vibrant O2 sensor spacers with the smallest orifices, and it's running fine with no CEL.
Idle and normal driving around you can't really tell a difference, but at WOT it comes alive and screams now! Should be even more fun on track days now.