Try breaking it down into pieces - There are several texture maps you need - Diffuse, reflection(the two weaves have different values), gloss( again different values), bump and a shiny transparent overcoat..
Man, Epic. I just have one suggestion. The carbon fiber looks great but it seems to me a pretty standard weave and Pagani has almost a "signiture" carbon weave they use pretty exclusively. Each weave thread is just as wide, they're just longer.
Thanks, the Zonda's weave isn't that dissimilar with the standard stuff pattern wise, really hard to tell the difference from this distance. The major difference is in the titanium material, it has sort of rough shards in it that give it that rough, noisy look as opposed to the lighter grey shade.
I just took a look at the interior render. It looks like you have the CF nailed down in that one. Maybe its just the scale of it on the exterior thats making it look more like a standard weave. anyways.. its amazing regardless.