I only heard of one company that was producing a header:
http://www.coloradofans.com/viewtopic.php?t=44539&sid=f4e09eefde2910a87d71e81a 3eac0676
Or, you can gut the cat from your exhaust manifold and get pretty close to the same gains from a header and retain the stock look:
http://www.coloradofans.com/viewtopic.php?t=38793&sid=f4e09eefde2910a87d71e81a 3eac0676