found this internet site interesting.  
http://www.rri.se/index.php?DN=29656 different vehicles, 1 dyno (hub dyno so accurate), 
and comparison graphs of manufacturer stated output Vs actual output.  Quite alot of surprising on the outputs and confirming what people thought about the likes of the focus RS etc
all the below are with reference to the manufacturer claims
Golf edition 30 8 Hp under 
Golf GTI 5Hp under 
mk6 golf GTI TSI 5hp up
Golf R32 23Hp under
Leon cupra 11hp under
Octavia vRS 2Hp under
Scirroco R  2Hp up 
scirroco TSI 8Hp under
Audi S3 2Hp under
Audi TT 3.2 S tronic 30Hp under
so the TFSi engines seem to be pretty much on the money.  the V6 not so much.
now for the other hot hatches 
Focus RS is 20hp under 
Civic type R is 16hp 
Meganne RS250 18hp 
Focus ST is 9hp under 
08 impreza STI 30Hp under
Astra VXR  11Hp under 
Vectra VXR 38Hp under
Mazda 3 MPS is bang on the money,
Mazda 6 MPS is 7Hp above
Nissan 350Z is 34Hp under
can you tell im bored 

found this as well-
Top gear test track times
http://www.bbc.co.uk/topgear/show/powerlaps.shtml