Someone should trace the I2C lines back from this audio processor chip. SCL and SDA should have pull-up resistors somewhere to Vdd, and they should also be connected to a microcontroller. Since it's I2C, I don't know what else might be on the bus. Of course there may be more than one chip connected to these lines since I2C devices are addressable, but ONE of the chips should be the microcontroller supplying I2C master data. That would be assuming there's only one uC on the main headunit module that contains the firmware.

Here is the PDF for the larger QFP (with the two white paint pen dots):
Attachment 155813
It appears like this is the likely suspect.

I'm sending the information to another tech who programs components to see if this is something we can do in-house.

what happened jon! don't let the dream die!

I gave the data sheet to the tech who programs components... just waiting to hear back from him.

Might wanna ask mazdaparts.org - they offer HU software upgrades...

^Thought about it... just didn't think they would disclose that kind of information since its possible I could "compete" with them if I'm able to produce multiple chips myself.
Guess worse they can say is, "f*ck off"

I tried. He never even emailed me back.
I also emailed some other radio specialist types across the web without success.
The most i ever got back was that i needed to buy a new HU.