Quick question.... Any truth to this... take from

Jaguar S-Type - Wikipedia, the free encyclopedia

Later models of the S-Type R featured a revised pulley system for the Eaton M112 supercharger allowing it to produce an extra 20 hp (15 kW; 20 PS).

I own a MY2005 STR, would mine have this, and if so does that mean 410HP or 420HP?

 

Editorial error. Due to the addition of VCT Variable cam timing) in 2006, Jag made a rating change; from 390 hp @ 408 lb/ft trq. to 400 hp @ 413 lb/ft trq. I've read an addition to a revised twin intake throttle body made for more power?

 

Isn't it due to the revised SAE definition of HP and/or the change to ISO / other standard? Many cars also changed, for the same reason(s).

The pulley was revised because it was noisy and in many cases pully & drive belt replaced free under a TSB, such as S100-11 or JTB00045v4. Also see www.jaguarforums.com/forum/showthread.php?t=25596

 

jagv8, in regards to revision of hp/trq rating: I've read the same.