When I took over managing it, I recommended to the owner that he have an EDM fitted so that LOP could be done (the POH has it using the factory single point EGT but apart from a one experiment to see how it would run on an empty leg, and a single demo to the owner to show the fuel savings, I've never run LOP without the EDM). At the time I said GAMIs might be needed post-EDM but we should have a trial period to see. That was 7 or 8 years ago
Probably a bit late to start recommending GAMIs now. Anyway the engine is only a couple of hundred hours to TBO. Maybe post overhaul I'll revisit the topic.