True speed is a company doing true speed tests on several models to see the variance on the supplier figures. This is also done at altitude +- 1350 m.

The performance results not to bad for a detuned S3 at altitude. Have a look :

Audi S3 2.0 TFSI Quattro S tronic

Also see the test on the C63 for example :
http://www.truespeed.co.za/index.php...rformance-pack