A8L Surging
 

A8L surges while coasting between 50mph and 30mph, any recommendations?

Post this in the appropriate A8 forum. A year and engine would help. There are 3 chassis to choose from too...

After that, try checking for vacuum leaks, and clean the throttle body and scan for fault codes!

...'Performance and Tuning' generally relates to performance enhancements and modifications, not how well your car is driving, which is a maintenance issue...

What he said.......scan for codes! Otherwise you are just guessing!