Okay, did some re-coding of the MAP sensor support. Unfortunately, that led to some code bloat. The code was at about 17800 bytes when I finally got it to work as I wanted. So I decided, "Aw, hell," and coded in a few more things that I thought would be nice.
So, now, the stored parameters now reflect whether the MPGuino is in metric or US mode. The displayed parameter labels even change, based on whether metric or US mode is selected. Also, it is now possible to calculate that "microseconds per gallon" value from within the MPGuino itself. All you need are the number of injectors in your vehicle, the injector rated flow rate, and the injector rated fuel pressure (which is normally 43.5 psig, or 3 Bar).
(cut/paste
type? Geez...)