Step-back Exhaust/ECU

I've got a bit of a weird wiring/computer question.
I have a 2000 cherokee, with that evil $1300 header/dual cat/dual O2 sensor setup. I'd like to step back to a 1999 ECU, single cat/O2 sensor, and with the header separate from the cat. I don't have it registered in a california emissions state, but one is on the border, so it had to meet specs when it was new. If I were to buy a new 1999 exhaust from the headers on back, what would I need to scav from a junkyard to prevent a constant 'check engine' code?
Thanks for your help!

I researched the same thing. What you want to do it illegal. It HAS to have what it came with from OEM. Whether that gets checked or not is a different story. You'll need a new PCM. Problem with that is Chrysler has the VIN "burned" into the PCM. That's not reprogrammable. But for around $1100 you can get a new one with your VIN on it. That's really about it, either way you're going to dish out a huge amount of money.

I had a sneaking suspicion it was a little in a grey area, but I didn't realize it was illigal in a non-cal emissions state. Interesting. What about wiring? Do you need a '99 harness too? or just not connect one of the 02 sensors?
I'm not only interested in this to avoid buying the stupid cat/header, but also to be able to use higher performance exhaust components, which seem to be either nonexistant or ungodly pricy for '00 and '01... so the money would be well spent on a PCM I believe.
Thanks!

Unsure of the legality, but you could also change to 2000 non-California style. Should be able to get the exhaust header and ECU/PCM on craigslist from someone dismantling one. Not sure if the VIN has to be burned in.

Any altering of the Stock emissions is considered illegal.

I have a Focus that uses all the OEM SVT exhaust it's thge same as the stock exhaust on the SVT focus model but does not use an EGR. Even with OEM equipment since I am not using my EGR (which came stock, but not on the SVT) it becomes "illegal" or at least not approved to be registered as a street vehicle.

Fair enough.
Would you still need a full harness off a '99, or just leave the 2nd O2 disconnected?

Non California Emissions 2000 and 2001 XJ's don't have all the extra crap on the exhaust manifold, just a single cat converter and two O2 sensors.