I believe that the accuracy of an i3's speedometer can be coded to so that the speedometer will display the actual speed rather than default several percent more than the actual speed. However, an Internet search hasn't turned up how to do this on an i3. If you know how, please post your method.
[22-04-25 to now] 2019 BMW i3 Imperial Blue Metallic, Giga World, Tech + Driving Assist, Heat Pump, 428 Wheels
[14-11-05 to 22-06-15] 2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging