Try this: http://www.o2simulator.com/4436.html
Its a device called an O2 simulator. Basically you hollow out your cat, throw your O2 sensor in the trash, and install this little device to the wires that would have connected your computer to the o2 sensor, and your computer is tricked into believing the cat is still there and functioning.
I think its probably a better idea just to remove the cat and save it in case you need it. If you hollow it out, its just a worthless rattling shell. You can pick up an old one from from a scrap yard I'm sure, and just hollow that one out, rather than messing up your factory one (in case you change your mind, or need to sell, or need to pass an emmissions test).
I still have all the original parts from my truck, as I have replaced them with bigger and better aftermarket parts. You never know how your needs will change 6 months from now or 6 years from now. By the way, you may want to take a closer look at your exhaust manifold. On my 2004 Tracker there are 2 catalytic converters. One is located along the tailpipe just beyond the exhaust manifold. One is BUILT INTO the exhaust manifold. The dealership called it a "pre-cat" and basically it looks like a tiny little cat. The two cats work together to reach the emmission standards of the nation the vehicle is being exported to . I hear in Australia they dont even have cats on the exhaust systems.
All this having been said, you can pick ap a low restriction cat from a good manufacturer like magnaflow for under $200 Canadian. I did this because we have to pass emmissions tests every couple of years here in Canada.
