What can/should I do to my exhaust system?

I have a ‘90 Pontiac TGP with a couple of mods on it (computer, new air filter, fuel injector swap). It sounds very, very nice. If you can put your ear up to the exhaust tip the whole drive.

So, yes, I am asking how to make more noise, and that’s all. I don’t want to get rid of the cat just because I don’t want to make my share of hole in the ozone any larger, even though Alabama doesn’t have mandatory emissions testing.

So, could I just take my car to a shop and say, “make it louder,” or would I have to do this myself, and if so, what kind of process does this entail? I can probably take it to a shop class at a tech center I attended last year and have all the tools and shop equipment I would need, as well as the educator and the extra muscle to help. What kind of parts would I need? How much should this job cost?