George

Don't forget that disconnecting MAF will log fault codes and put the ECU into a default strategy, e.g Possibly disabling the EGR etc.

So what is the EGR doing at the same speed with MAF connected / disconnected

what is the actual flows rather than requested?

You could be correct but I'm not convinced that The MAF has that much influence on fueling on this system, possibly EGR monitoring and (black) smoke limiting at high load / speeds only.

A diesel engine at low load should be running with a surplus of air so what effect would adding extra diesel have ? ?

Cheers Aidan