What are common issues with the Audi A2's engine and how can they be fixed?

I recently purchased an Audi A2 and noticed some performance issues with the engine. I want to know about the common issues with the engine and how to fix them.

One common issue with the Audi A2's engine is a dirty air filter. This can decrease engine performance and cause issues with fuel efficiency. Make sure to regularly replace or clean your air filter to avoid this problem.

Another issue to look out for is a faulty oxygen sensor. This can cause the engine to run too rich or too lean, resulting in poor fuel economy and potentially damaging the catalytic converter. Have a mechanic check and replace the oxygen sensor if needed.