Where do I get an upgraded ECU?

I have 1994 Chevy Camaro and I'm looking for ways to get more hp and I was told to get an upgraded ECU. Where do I look to find one and who can install it? My fiance has some friends that work on their cars but I don't know how difficult this would be... Getting a new exhaust system from headers back would be nice, so I am looking for that too, but in dual form. Help me! I live in Kalamazoo, Mi if that helps...