Yeah, with an open diff it would just spin up the inside rear which is okay (although you should still be able to get it sideways with an open diff I'm sure), but then stick an LSD on it and it would spin up both rear tires without getting sideways! Hmm....
Fortunately if that updated version of GT4 for the PS3 (with new graphics and physics) is anything to go by, they've fixed that MINOR (haha) flaw and improved the driving experience a bit more for GT5. Should make it fun enough to enjoy lapping the 'Ring in a Ferrari at least...
Back on topic, no you can't get a sim version of pikes peak, but you can drivce the Escudo on a small and very watered down Pikes Peak in GT2 and Rallisport challenge iirc
Oh well i'm extremely sorry for making this awefull mistake, that is quite clearly one that is never made and should never be made as you clearly proove you'd have to be some sort of clinical genious to work out I was talking about the allmighty km/h.