Rare for the head gasket to go, good luck with the rebuild.
A lot of people have said that its between 2-3 it's lost 30 psi in 3 over the rest.
Should be ok mate I work for a Porsche specialist but don't know all the funny French ways of this engine
Aston's are a pile of s**t eh! brake pressure switch on AMV8, gearbox over heating on DB9's, engine mounts, rocker covers, cracked plugs, oh and clutches!