This one doesn't seem to be official in any way, rather belonging to a very enthusiastic car owner, and seemingly a GTA fan judging by the 'classic' style GTAIV logos and Rockstar decals. Apparently this nice machine was spotted at the New York Auto Show. I'm not a great lover of cars with black paintjobs, but this is something a little more decorated than usual.
This just got me thinking, would if a Nascar team was sponsored by Rockstar and it had the Rockstar logo with the "IV" logo all over it...that'd get some attention. It would also get fans to go "Holy shit!!!, this means racing is a big part of the game. BLABABLABLA!!!"