How much loss for rear mount turbo?

according to these guys turbo lag for rear mounted hair dryers is a myth. I remember watching them do a camaro on TV with the STS kit...
[ame="http://www.youtube.com/watch?v=rdjh3EY6shU&feature=related"]YouTube - STS Rear Mount Turbo Lag Demonstration[/ame]

[ame="http://www.youtube.com/watch?v=13cvNXQOCjo&feature=related"]YouTube - STS Turbo Corvette on 2 Guys Garage[/ame]