i don't know the answer to the cat problem, but if i had to smog my beast, i would shelf it until the day of smogging...remove and shelf again. IF...it can go bad and does, go buy one then for the 70 bucks mentioned above....well thats what i would do.
I don't know about your state, but MD has historic tags available for vehicles over twenty years,...which means no smog. So i just tagged my 4Ruster historic, but you may have an issue if this truck is your DD...i guess.
I have removed my cat and muffler...straight 2.25" pipe to glass-pack dumping out in the stock location...sort of. It isn't bad idleing, but it is louder on gas....kinda has a fart can ricer sound now, but this is temporary till the 1UZ goes in(next year).
If you run just headers, it will sound like a tractor as mentioned above....i had an old downey, and that bitch was LOUD....not fun.
The O2 stays on the manifold on the 22re, so that shouldn't be an issue unless you get a header that doesn't have one.

RB

 

Who says a cat can go bad? And what is wrong with the cat n muffler on there. Just muffle it and be done with it, nothing worse than an annoyingly load yota.

 

Mak92- how did you get away with cutting off your cat in CA? that is a good magic trick if you pass CA smog without it

 

I removed the muffler today, left the cat, replaced it with straight pipe...it's not really THAT much louder on my 3.slow. I notice a little more oomph

 

Just to note, my 40 year old JD 1830 tractor, which I believe has a 67hp diesel in it (4cyl), has a muffler on it and isn't very loud at all until you get the RPMs up for PTO equipment, but with it at low-mid RPM my truck makes more noise idling, and that is missing the cat but has a muffler (a stock-style one I'd guess, it's a big cylinder with the input on the bottom and output on the top on opposite sides). Actually, if I get the truck up to about 3k rpms in neutral (because how can you compare if either is moving around) it can drown out the tractor unless the throttle lever is cranked and the pedal is down (a pretty rare occurrence with my tractor). Now the smell when you start it in the middle of winter is an entirely different matter, I can think of few worse smells than raw diesel exhaust, especially when you have to let it run a little bit before driving and it fills the shop with thick black smoke despite the big garage-style door being open, my lungs -really- enjoy it.

My JD 2305 mini-tractor is super quiet as far as tractors go too, most passenger vehicles are louder unless the mowing deck is on it, then say goodbye to your eardrums if you don't wear earplugs.

 

a friend of mine cut his muffler out of his 22re and just ran a pipe back from the cat. I really didn't think it was terribly loud as we were driving around in the woods, although i was following along behind in my truck. still i can't say that i remember taking much notice of it while parked at idle beside him either.