Fuel System Leak Test
WARNING: This page is about a different car, the 2016 Audi A6 Quattro. However, it is still accessible from the selected car via links, so may be relevant.
Procedure
-- Let the engine run a few minutes at a moderate speed.
-- Turn off the ignition.
-- Check the entire fuel system for leaks.
-- Replace the part if there are leaks in spite of correct tightening specifications.
-- Perform a road test and press the accelerator pedal all the way down at least one time.
-- Then check the high pressure area again for leaks.