Is it allowed for the software in both EECs to be modified, or just reloaded, before a flight?
That would seem to be in the same category as checking all MCDs at the same time.
Unfortunatley I believe not i.e both FADEC's can be replaced at once if required.....IIRC Having replaced FADECS in past for software revision they had to be replaced as matched pair.
Any revisions might effect such things as EICAS warnings etc...so It would be logical to have both engines running same, otherwise very confusing to the pilot
I seem to remember all that was required was an Idle run and computer download to check for any generated faults. At least as a flight control they would need duplicate Inspection for fitting so I suppose that is one up on a MCD Installation etc...