Can anyone identify this tapping noise?
Interesting videos.
The injector balance is all within normal range even though 3 are high and 3 are low (this is 3 injectors offsetting the other 3).
The slo-mo video clearly shows the loud clunk is in time with one of the cylinders firing. In slo-mo my TDV6 has the same beat to it, but the leading beat is not a metallic clunk like what you are picking up.
I wonder if you have a sticky valve that is slamming shut, or a roller valve rocker with some play, or hydraulic tappet that has collapsed and not fully opening. Maybe time to remove the inlet manifolds and look for something loose, and then rotate by hand and make sure all the tappets/valves are moving freely.
Pity we don’t have the option to remove rocker cover and run the engine to diagnose.