AudiForums.com - Just bought a '97 A8, got some Q's

He's right. Unless you're a tuning genius who has his own shop full of equipment, and a deep-seeded urge to doit yerself... You're mostly limited to:
-Tip-chip (goes in your tranny, but, from the pics you posted, yours doesn't appear to be a tiptronic)
-GIAC, or similiar, chip for your motor. Good for maybe 10-15hp. $750-1250 (installed, depending on who does teh work and what part of the country you're in)
-Stainless-Steel exhaust. Good for 15-25hp, give or take. Figure on $1250-$2000 (same as above)
-Various suspension mods. everything from lower springs to a neat airbag setup I plan on eventually getting for MY D2. Anywhere from a couple hundred to a couple grand, depending on what you get and who installs it
-Some sweet wheels (if you happen to be one of those who refers to them as "rims," STOP IMMEDIATELY!!! They are called WHEELS!). Your limits are governed by taste and your wallet. Goto www.edgeracing.com for some decent examples and reasonable prices.
-Tint
-Phatbox (if you have the CD-changer in your trunk. $170+shipping, on ebay, when you can find it.
-Armrests from a 2000-2003 (they're a VERY NICE upgrade from the ones your vehicle came with, and, if you keep calling around, every other week, or so, for the next year, or so, you may be lucky enough to find a set. There's a write-up on AudiWorld, I think, on how to go about replacing them)
-M5 type rear-lip spoiler. If you get this make SURE you get it painted to match your car... PLEASE!!!

Anything else you you do would be retarded and we'd be forced to send out a hit-squad to flatten the TOPS of your tires (yes, they're JUST THAT GOOD!!!).