I have recently purchased a 2001 Audi A6 4.2 Quattro. What are the best performance upgrades I can get for it? I'm not looking to spend over $500 which I know isn't a lot but it's a start.

 

The best upgrades for a car this age are: new mass airflow sensor, new plugs, new oxygen sensors, new air filter and fuel filter, change to synthetic oils and lubes. These changes can add back lost power caused by the gradual degradation of these devices. The power loss can be around 20% which you can get back. No other upgrades in this price range will do near that.

 

What kind of spark plugs to you recommend using? Sorry for the questions, I'm totally new to Audi.