Ok. I'm. best to answer this since i've had both versions(and heavily modified both) of the rear bumper and rear sport kits for quad exhaust.
Several misconceptions here. The 04s are different as the skirt apron that simply goes on top of the stock bumper. The original OEM 04 rear sport kit comprises of a lower valance/skirt that has detachable exhaust panels. Each panel is riveted on with pop rivets. There are 2 panels, the exhaust on the left, and a blank on the right.
The 05-07 sport valance is a lower skirt that is installed by removing the stock lower valance via the tabs. The Sport skirt is entirely one piece, and shaped similar the the 04, but the panels are non-removable.
The other option is to simply modify the rear skirt with body work and simply cut out the sport valance to fit your quad setup.
To install the VIVA exhaust panels on an 05-07 bumper, some custom work will be necessary to cut out existing panel and remove the exact shape and the tab areas to allow for the VIVA exhaust panel to be placed in the same spot, the panel would then be rivetted in place.
