Nope, all the alterations are able to be made from the MPGuino its self. In the setup screens you can change the usec/gal (microseconds per gallon) and vss (vehicle speed sensor) readings. If you want to adjust them to imperial gallons and imperial miles the MPGuino doesn't care... to it they are just numbers. There is also a
kit, but last I knew they were on backorder. You can get a lot more information in an organized fashion at the
wiki.