Why do Corvettes have such a SLOW top speed compared to the competition?

[sal]

I mean take a 638 BHP Corvette ZR1. It only edges out an old 2001.5 270 BHP 4000lbs Volkswagen Passat W8 by 30MPH at the top end.
http://www.youtube.com/watch?v=6ygtAzz9yhw
Even ANCIENT cars with FAR less power like the Ferrari F40 have a similar top speed as the ZR1.Even Luxury cars like the VW Phaeton W12 or the Maybach 57S will beat if not CRUSH a car like a Corvette Z06 at the top end if you remove the governors on all of them and see how fast they can go.
http://www.youtube.com/watch?v=KmGNRMOpg7E

Why is a ZR1 SOOOOO far behind older technology like the Mclaren F1, Enzo Ferrari, or Pagani Zonda for example even though it has the same kind of power as them, but as far as the top end is concerned, the ZR1 will be left light years behind in a place like Bonniville.