My old Buick was a sleeper...
http://a49.ac-images.myspacecdn.com/01498/84/08/1498658048_l.jpg
People didn't really know what it was, because it's not black. Was a really fun car though, never ran it at the track but on low boost it felt like a low 12's car, full weight with everything working. Turn the boost up and it was mid 11's easy.
The Supra, definitely not a sleeper, nor could I ever make it that. The only thing it has going for it in that regard is that I'm running upgraded 12b's. That look stock, and I can say and do say they are the stock turbos for that motor, b/c most people don't know the difference.
And yes I have a thing for dark gray colored cars.