Valves, Checking
WARNING: This page is about a different car, the 2022 Audi S3, 2022 Audi A3 Quattro, and 2022 Audi A3. However, it is still accessible from the selected car via links, so may be relevant.
-- Check the valves at stem and seat surface for wear grooves.
-- If there are clear wear grooves, replace the valve.