First off it is good to see a pilot paying attention to what the engine gauges are reading.
. Thanks for the kind remark BPF. I was surprised I'd noticed as well, but perhaps I'm more tuned in than usual having also had an oil pressure failure (in a different aircraft) this year as well.
It is a -161. It's had at least one fuel pump failure in the time I've owned it, that was an obvious one way street and otherwise the pressure has been rock solid until now. I suspect the issue might be more widespread than generally recognised, based on the number of forum threads that describe similar symptoms and then write it off as 'normal behaviour'.