Jaguar XF 2010 3.0D DTC P0401 EGR Issue

Hi Folks.
Wondered if any of you good guy's out there have come across this?
Jaguar XF 2010 3.0D P0401 EGR system insufficient Flow detected.

This is a V6 with 2 EGR valves.
My initial live data 'anomaly' look has found @idle the
MAF bank 1 @10Kg/Hr
MAF bank 2 @100Kg/Hr these are approx, but you get the idea
Identical MAF sensors......when swapped, readings are approx the same.
When rev'd the bank 1 is reading approx 6-10% of bank 2.
Having no experience of this engine or the 2.7V6 JLR/PUG unit... i am open to thoughts of whats going wrong here?

HOW do you diagnose which EGR is in trouble?
Does the system use Map sensor also to 'detect' low EGR flow?
Everything looks a pig to work on on these!

Also... the air filter looks original! Blocked solid with crud @55K, took the oil cap off and full of black sludge! Criminal Neglect of a nice machine!

All Help appreciated.