That is great!! I have a 2007 GX 470. The steps where not exactly as written in my situation but it got me into the hidden menu. There was no Bluetooth under the navigation service button but there was a "Hands free Voice quality Set" page where one can make adjustments. You can adjust " Receive Voice Level" " Send Voice Level" and Voice quality Type.
I set them all to 3
Any help on this?
Thanks
MV