Just a small tech note/FYI as I recall there being disagreement over the exact detail before. I cannot comment on relevance to pre-facelift Xantias.
The wiring plugs are held in on the scuttle side with one centre T20 headed screw each. This is very deeply recessed; I used one of the "L" shaped Torx keys to loosen. Before loosening the centre screw on each one, pull up the yellow security tab between the individual plugs, or prise it out altogether - it will come away without breaking. These screws within the multiplugs are captive.
Xantia II Bulkhead Wiring Plugs
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