When my wife drives either car BRZ or Corolla she gets about 20% worse economy than me driving round city.
I can get better economy driving much harder
She generally drives like a nun , but she holds gears too long both our cars are manual 6 speed
When im just crusing i will be in 5th or 6th light throttle where wife will still be in 4th maybe 5th
driving style makes huge difference
check out your Open loop fuel table example below, when your crusing arround you need to be trying to keep in the areas with highest afr. ir low load low rpm light throttle.
http://i.imgur.com/6W3B1GH.png