rickymp

? same as S8 or RS6/7 with a differnet tune; or are the higher output engines beefed up to handle the extra load?

DeerHunter

Beefed up. There are threads on the subject if you care to search.

Austintex

At some point in the past someone helpfully posted the engine self study book, which explains a lot about the engine, including the differences between the S8 version and S6 version. I would try searching for that if you want details. Good luck.