I suspect that all this boils down to a debate between those that use engine monitors v those that don't. One doesn't need to be highly educated to understand the information that an engine monitor provides. Only a bit of simple mathematics and common sense is required.
tio540, I encourage you to go for a flight with someone who uses a monitor and has done an APS course. And for that person to explain all the 'black magic' involved. You may have a change of opinion running your engine then.
