closed loop should be bouncing the AFR's from lean to stoich.
i think its like 10 times per minute or something, not just sitting in the stoich area on the guage..
i think the condition affects how responsive the unit is.
Bluer33 - safc would allow you to tune the ECU beter for more economy as the std maps are fairly rich when your giving it to the car..
gaps would only help if they are wrong and not the correct gap.. most people run 0.8 for under 1bar of boost.
dont think a dump would help economy too much, except that it would help with power, so less throttle to do the same as before.. so yes it might, as long as your right foot is in check.