How to fix poor acceleration issues in an Audi 80?

My Audi 80 is experiencing a sudden loss in acceleration and is not performing as well as it used to. I've tried changing the spark plugs and air filter, but the issue persists. What could be causing this and how can I fix it?

One possible cause could be a faulty fuel pump. If the pump is not providing enough pressure, it can result in poor acceleration. It is recommended to have a mechanic check and potentially replace the fuel pump if needed.

Another potential issue could be a clogged catalytic converter. This can restrict airflow and cause a decrease in engine power. Consider having the catalytic converter inspected and replaced if necessary.