I will get them to disconnect the exhaust system at the Cat by-pass pipe to see what happens. I should mention that the middle box has also been removed by the owner during the service. Interestingly, I Autocom'd both vehicles to compare figures and the only difference I could see was in the Airflow figures. In other words, the boost pressure was the same for both vehicles...unless I overlooked it.
Will let you know nonetheless. Many thanks again.
Regards
Pete M