What are the most common issues with the Audi A8's engine?

I have recently purchased an Audi A8 and have noticed some unusual sounds coming from the engine. I am concerned about potential problems and would like to know what are the most common issues with the Audi A8's engine?

One common issue with the Audi A8's engine is carbon buildup on the intake valves. This can lead to reduced performance and potential engine misfires. It is recommended to have the intake valves cleaned on a regular basis.

Another common issue is oil leaks, especially from the valve cover gaskets. These leaks can lead to low oil levels and potential engine damage. It is important to regularly check and replace any worn gaskets.

Some owners have also reported issues with the timing chain tensioner, which can cause a rattling noise from the engine. If you notice this noise, it is important to have it checked and replaced if necessary to avoid potential engine damage.