DAR
You raise some good points. One clarification: I did not mean to imply that an electronic fuel flow meter be used for leaning, rather that if you "have" to spend some money on an electronic gizzmo a fuel flow meter is a worth considering because it will give you accurate indications of fuel used and fuel remaining (if properly set at the start of the flight) which will be more usefull than the pathetic fuel guages. The Robin has a fuel pump but your caution about fuel flow meters in gravity feed fuel sustems is however a good point.
I am still not convinced you can consistantly get an engine to run significantly more leaned with a multiprobe EGT than by the old lean to roughness method. The engine diagnostic capabilities are real but IMO not alone worth the cost of the advanced EGT systems. I think a multi probe CHT is of more use because IMO excessively high CHT is a far more widespread problem than sticking valves, and will usually reduced cylinder life. The only other way to detect a too hot engine is oil temp, but by the time the oil temp has spiked you will have allready hurt the cylinder. CHT will also show deteriorating baffles, a common problem