Cars with after-market accessories (e.g. remote starters, alarms, etc) generally have modifications to their electrical systems. Automatic is an after-market product that requires a functioning unaltered electrical system. Because there are so many possible scenarios that result from installing after-market electrical devices in a vehicle, we cannot guarantee normal functionality if your car has one of these modifications.
Additionally, we can't provide any troubleshooting advice or extensive support since there is no guarantee that these after-market modifications were installed properly.
In terms of engine modifications, MPG calculations may or may not be accurate. Automatic should calculate accurate MPG if the changes performed were only minor bolt-on air modifications. If, however, a modification was made to the fuel injectors or something else that would change the fuel map, MPG will be inaccurate.