Electronic boosting might involve raising the output voltage going to the transmitting antenna.
Or, raising the gain of the receiving amplifier.
I do not recommend trying to make modifications inside a working unit. You might stop it from working at all.
Adding a directional antenna, to both units, is probably the wisest option.
Also try not to put any metal structures between the units.
Operate on a channel which is unused by anyone else.
Set an option for slower transmission speed. This could maintain reliable communication in conditions of weak or distant signal.