It has honeycomb inside of it. It heats up from your exhaust and once it's up to temperature it chemically scrubs the exhaust. Basically it gives you less emissions. What usually happens is that the metal inside starts to deteriorate and the honeycomb collapses. That's when it starts to block the exhaust. That's my understanding of the convertor...cats 101 as it were. Here is a good place to check it out... http://auto.howstuffworks.com/catalytic-converter2.htm
A cat convertor on its way out is usually accompanied by the stench of (rotten eggs)its actually the sulfur in the gas not being scrubbed out.Bang on it and see if it rattles.If it does,replace it if it dont you may have to visually inspect it to see if its plugged unless you have access to exhaust pressure sensing equipement.
could this be steam comming out of the rad or a hose somewhere? when im under the hood tuning my car of coure the air cleaner would be off. when it is in makes a constant wossh sound as air is being sucked in so it may be an issue with that. but if your in your car driving i doubt you could hear that.
one time one of the bolts that holds my carb on came loose and my car sounded like it had a turbo..:bananaman
Thanks for letting us know. To fix the problem you have a couple options...clean it out or you can eliminate it if you know someone that works at a small neighborhood type exhaust shop. Franchise shops likely won't help you bypass it because of the legal ramifications. You could always try doing it yourself but that's not an easy task if you don't have the right tools and will probably leak like hell. You can always have a new one put back on...anywhere from $200-$400! If you try to clean out your converter, you'll probably have to take it all the way off the car. It's a tough job breaking up the honeycomb material and getting it out...unless you're lucky and it's already all broken up. It is possible to clean it out and I would likely try that first before I did anything else. I have done a couple of them with success. Good luck