Seeing this is your first post here Hello
and welcome to the European Forum Chris !! (even managed to beat Joe to it !!)
I'm not sure if anyone here has messed about with the remote locking and keyless entry system. For certain our car has the remote locking linked to the Cobra aftermarket alarm system but I've not had to investigate it.
Are you trying to fit a new standard Subaru system or an aftermarket one ?? The wiring diagram you have, is it correct for the year of your SVX (although I can't see the colours changing over the production run.......maybe !). Is the diagram one a genuine subaru one or one from a manual like Chilten or something ?? I guess what I'm trying to say is do you trust the wiring colours ?? What colours do you have on your car ??
Sorry not much help really, more questions than answers.
Phil.