congrats on the decision to buy an Audi A4.
You ask about Mods for the A4, have you picked up an issue of either
European Magazine or Euro Tuner lately?
Both of these mags have multiple stories about Audi A4's being modified, so I'm sure You should have NO problem finding article on this.
You don't say where you're located, but over in the SF Bay Area,
Jim Osborn has a shop, Oz Sport Tuning.
Jim has seen 300hp in his VW Jetta, which shares the same Engine that
the A4 would have, the 1.8t.
Let us know & let us see the pics when you get your A4.