I don't see anything wrong with the rear end itself. Although that spoiler doesn't work at all. Also, the car wasn't finished in that clip.
I can't find any more info on either of the two cars.
How's this for INSANE. E30 with 3.6 M5 Twin Turbo making over 1000bhp!! (I'm sure some of you might have seen this before)
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Some picks of the madness!