What is the most common cause of poor performance in an Audi 80?

I have noticed a decrease in my Audi 80's performance lately and I am wondering what could be causing it. Can anyone shed some light on this issue?

The most common cause of poor performance in an Audi 80 is a dirty or clogged air filter. It is recommended to replace the air filter every 15,000 miles to ensure optimal performance.

Worn spark plugs can also lead to decreased performance in an Audi 80. It is important to regularly check and replace spark plugs to avoid this issue.