VE a6 to m6 conversion help

Hi Guys , trying to get a customers vehicle runing he has changed it from a6 to m6 and has changed the loom to a manual loom etc i have found a manual tune to use with the same operating system as his old auto tune (which i had tuned prevous) v2 will not conmunicate thu the ob2 port and has a heap of fault codes on dash but when doing a vehicle scan for can - bus (with other scan tool) it can't find the ecm , auto trans etc so i removed the ecm and flashed a manual tune in to on the bench but still no go i'm guess it has a break in the can-bus network some where are the manual wiring looms different from year to year? my operating system number is 12635863

How did you go with this??