Personally I'd change to a aftermarket ecu, 3d mappable of course.
These ST engines with the variable cam can produce awsome mpg figures, indeed as much as 40% reduction has been noticed on cruising throttle settings, some people have experimented with this on certain rollers with the feature turned on and off, mapped for max power on each.
Net result was no power loss with it on, but torque gain with it on, and a massive up to 40% reduction in fuel needed under cruise type conditions, maybe the ford ecu isn't that good to take full advanatage of what's on offer.
tabetha