I wanted to pass this along:
I just replaced my Cat. converter on my '89 K2500. I replaced it with a model from "extremeflow", only cost about $125.00. These are high flow and less restrictive then the OEM converter and they claim it will give you a 10% boost in horsepower and torque. I must say, it did make a huge difference in power and I passed emissions.

I've heard some stories about the high flow models not working well enough to pass emissions. I didn't have that problem and the installation was pretty easy. I had one 18" pipe bent at a muffler shop. The new converter is tiny, about half the size of the original.

If anyone's needing a new cat. converter for emissions or to improve performance, this brand worked for me. It was considerably cheaper then the OEM option.