Thank you Matt and Aiden for you input,we ran the car on our dyno this afternoon and can normally identify leaks underload,but in this case no leaks heard.We were fortunate enough to be able to take a power measurement 77.5bhp [spec 80bhp]and measure air mass meter output 4.2V [full load]momentarilly before the fault set in.
Considering that maybe the egr valve is sticking open causing a depreciation in air flow across air mass meter and the ecu interprets this as a air leak.Customer has taken vehicle away now and returning next week,keep you posted.
Thanks Trevor.