If you are talking about the textured leather grain black area, that is fiberglass. The best wax that I have found to use on all of the fiberglass textured area's is Woody's Wax. It comes in a metal spray bottle and is very easy to use and does a great job bringing it back and protecting the finish. Just follow the directions on the back of the can.
It is very expensive, about $40.00, but will last for years as it takes very little to do the job.
when i purchased my 03 from lee, he told me about this stuff and i was a little hesistant on spending $40 on a 16oz spray bottle, but a little goes a long way and boy does it make that textured surface look new!
Dang, had I known I would have brought my rig back last weekend. I normally just leave it up at DCL this time of year so I don't have to haul it up and down the mountain. Do this again in the October, that's not even an hour drive for me.