interesting question (can one parallel devices to one sender)
the "power" comes from the devices (gauge & EFI). since they both get power from the battery, they would SHARE given the sender will draw current based upon the temperature. therefore neither device would sense 100% of the current (which is what it uses to determine temperature)
or as JFFR said, NOPE
(or maybe, but with some consideration after performing a whole lot of testing and measuring))