So in that situation we would revert back to old school using the TIT probe and lean the engine to peak egt and then richen by 125 degrees at say 65% power.
You might earnestly believe and hope that that's what you're doing to "the engine", but you wouldn't know what's happening in each cylinder. However, you will have the warm inner glow that the regulator will consider you to be 'legal'.
Does a jpi monitor qualify for original aircraft certification?
Depends on the model.
Not sure, still I wouldn't remove the TIT probe hence its still there as backup.
I keep the original CHT probe and gauge for ****s and giggles too. I'm reminded what a joke it is every flight, because it rarely reaches the bottom (cold end) of the green arc, yet my hottest cylinder is much hotter but happens to be located on the opposite side to the original CHT probe. I reflect on how much safer I would be, and still legal, if I were flying blissfully ignorant of the fact that #6 cylinder is about to depart the crankcase.
I am just trying to get a picture of how we would advise casa we could comply in the case of a engine monitor or probe failure, and what goes in the Ops manual. Obviously we can't always cruise at the same level or power setting due maybe traffic or a crossing time requirement etc, understanding casa only has to accept your method not approve it.
A very reasonable and justifiable concern.
I suppose you just have to pray that you find someone in CASA that isn't chock full of folklore. Lots of luck with that.