Any claim that includes "electronics" is BS.
RF(wireless) send and receiver simply doesn't work in a way where "electronics" can increase the signal.
You either increase the power OUT(transmitter) or increase the power IN(antenna)
If there was an "electronic" solution then you wouldn't need a large transmit antenna or any receive antenna, but you need both, and the lower the frequency the larger both need to be.
FM is pretty low frequency RF, using RF 87.9 MHz to 107.9 MHz, this is between analog TV channels 6 and 7, so in the VHF(very low frequency) band of RF.
The lower the frequency the larger the antenna needed, that's why the old VHF TV antennas were so large and the UHF much smaller.
Windshield(or rear window) antennas work pretty well, they can be longer(larger) than the mast antennas.
Longer mast antenna might be better than stock mast, the antenna part is actually in the upper part to get it away from the vehicles metal, it is also longer(bigger).
If this vehicle is the only one having an issue with local FM stations then I would suspect the antenna or cable of having a problem, or even the tuner.
Distant FM probably wouldn't be possible with any size antenna, FM travels well locally but does drop off pretty fast at it's fringe area