My 46 FX came 1/2 turn too rich on idle too.
I do not agree, though, that en engine should be able to run its tank empty and still be able to go full bore instantly. That is a slightly lean condition because in the air, and as the tank empties, you get leaner (too lean). It is perfectly normal, in my opinion, that an engine loads up a little bit if let at idle too long. All you have to do is put throttle slowly.

Has anyone tried a stall turn with a lean idle? IMO, I do lots more stall turns than waiting on the flight line.