So I'm 95% sure this works. Thanks to
dootsmasta at
everythignq.com.
Basically under
HKLM/Software/Motorola/BPCTRLR/WaveDev/BaseGains are all the volume settings for this phone, including earpiece, BT, headset, mics, etc.
Change
HandsetPathGain to 10 and you should notice quite a difference. It's only +2 than the default but it does give a little edge.
Works well on the
SpkrphnPathGain as well for speakerphone.
Post your results here. You'll need a registry editor and need to soft reset for the change to take effect (wait a minute before the soft reset so that it can be flushed to ROM from RAM).