I am still running the stock exhaust with the cat in place. I'm worried about messing with it and getting a loud drone while towing.
The 2004 does not have a cat. The 2004.5 does. The 2004.5 added a 3rd injection pulse to try to help with emissions or something. I'm perfectly happy with mine. At 105,000 miles I am still running the original front brakes. I had to replace the rears when a caliper stuck or those would be original as well. I'm getting ready to put new wheel bearings and u-joints in the front and upgrade to better shocks now too.