Now that the insults from one individual have disappeared, I have a question. Perhaps Brian if you're still around you might be willing to answer.
The device I've heard called the "economiser" functions exactly as you said, enriching the mixture a specified amount at full throttle (not necessarily full power).
I'm also aware of a power enrichment valve, especially in carburettored cars, that opens a second, larger bore, fuel jet in the carburettor at high power settings to overcome the limited response that one can get from a single main fuel jet over a wide variety of power settings.
Question - are the two functions actually the same, just called by different names? Sorry if it's a silly question...
As to the bigger picture of old aircraft, new aircraft, and lack of leaning skills - from the point of view of safety, single power lever engines with modern low fuel warning systems can't come quickly enough. I have read (sorry don't have a reference) that not a single C172 has been lost due to fuel exhaustion since Cessna fitted the "L FUEL LOW R" annunciator to the R models and later.
Thanks,
O8