DannyG123US

Not looking to pay an arm and a leg, preferably something with reliabilty and potential to be really fast

Kneale Brownson

91 with a 20-valve engine or subsequent S-cars with the 20-valve engine.

Mister Bally

Early D3 A8. Have the speed limiter removed. Look in my profile albums for really fast potential. If you want faster, get one with a W12. It gonna cost ya more, but even higher top speed potential if you get the limiter removed.

This is based on your "really fast" and not pay and arm and a leg comments. Although all of us have different definitions of those terms.

GroupBquattro

The 5 Cyl turbo motor that won rallies and races for Audi in the 80s are the best. Both 10v and 20V can be tuned to great performance and reliability is tops. If you have the money and if you're lucky, look for an urquattro, that is the Audi to have.

richard-tx

The 2004 D3 suffers from first year issues. Get a 2005 or 2006. The 2007 and later FSI engines have carbon buildup issues. All of the D3 have air suspension so expect to replace front air shocks every 150,000 miles more or less. Cost is about $400 per shock to rebuild. Everything on the car is electronic so expect some issues there. Other issues common the the D3 are:
trunk motors
door soft close

richard-tx

A well tuned 20 valve will meet or beat a W12 depending on conditions. 500 HP is reported to be easily attainable with the 20v (3B) engine. 700 hp less so.

-Treser-

http://www.treser.info 5 cilinder 2.1 liter turbo KG old school 10V engine, 350 hp in a 1250 kg Audi 300 km/h