That 'bad smell' just means that the catalytic is working. A cat is only bad if it clogs up or rusts out. The bad smell comes from the catalyst reacting with the unburnt fuel in your exhaust; usually under heavy acceleration. Do you have a check engine light on or something?
Your CRX was much older and less technical than your truck. It had one o2 sensor before the cat. New vehicles typically have at least one before and one after the cat. (modern V-configured engines often have double the sensors.) You could say that the one after the cat is something that they added to prevent people from tampering with the cats. i could be wrong, but i'm pretty sure the readings that they take can affect your timing and air/fuel mixture. i think it also provides input to the rest of the emissions system.
I had a 2001 Subaru a couple years ago that i fought with. i had a check engine light that would not quit. i tried everything; replacing exhaust manifold gaskets, o2 sensors, and eventually the cat. i bought an aftermarket "direct-fit" cat set for the car from Eastern Catalytic for just shy of 400 bones. After putting it on, the CEL would stay off for longer, but the so-called direct fit cat had one too many 02 sensor holes, and the cheap support broke off a week after it was installed. In addition to that, it also destroyed my rear transmission mount. i had headache after headache, and with lots of buyers remorse, i wished i had bought the $700 OEM cat from Subaru. i began trying to figure out a way to do away with the whole mess (cat and all) but due to the computer and the setup it had, i couldn't. i ended up just running the car with the CEL on. i sold it that way. The downstream 02 sensor was the problem. i wasn't the only one dealing with all of that crap. There are little units you can hook up to the wiring to fool the system, but they are very expensive and hard to find.
I can totally see the advantages of getting rid of a cat though. There are small, but significant mileage improvements, weight improvements, and longer exhaust/suspension/underbody part life due to lower temperatures. i could say the same for every piece of emissions junk on our engines today. i've resolved to myself that older vehicles are the way to go; the simpler the better. i like my '93 because it has crank windows, a manual trans, no EGR system, and it's simple to work on. It still has a cat, but then, nothing is as quite as simple as my '70 F250 was. i guess that's the price we pay for safety, saving the planet, convenience, and comfort. Also, it could be worse. It could be a diesel particulate filter/regeneration canister.
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