Sounds like a good-as-could-be-hoped-for outcome. And "yup", Brian is a true expert, glad you were able to get him on the case. One thing that sticks out to me (and I did it too) is that it seems like the definition of insanity to replace with OEM headers/manifolds (I too did that when my CS's pre-cat was failing). Both because of the high-cost and because, well, its literally "doing the same thing and expecting a different outcome". I do think these things seem to disintegrate at a too high rate (too high for me anyways) and we all should be switching to replacement after-market headers. I paid iirc $6500 for one side only replacement header for the CS solely because I was selling it soon afterwards and wanted it to be OEM for the next owner. But if I was keeping it, no way would I put the OEM headers back on it (especially if it were a regular 360 and not the bit-more-collectible CS where OEM arguably has a bit more value).
I'm right there with you. There are no legal alternatives in my state though. I might be insane, but I'm no scofflaw.
What if you install oem headers w cat material removed. Then just run the oem cat pipes. Should pass visual and obd2. You can have cat readiness tuned out. I guess in the end you are right... quite a bit of work to do the above.
That's a shame. I replaced the stock headers with Fabspeed headers and blankets, and in combination with the OEM vlaved Challenge exhaust it wails like a banshee. Best five valve sound I've heard yet, and a huge load off my mind. Plus no CEL!
Apologies for the thread resurrection. If ever there was a case for taking your car to the best qualified repair shop, rather than the nearest repair shop, the OP's tale is it. This too shows what effect using the nearest and easiest shop can have ... : https://ferraris-online.com/dont-let-restorers-go-to-school-on-your-car/