An interesting development. Removed the RCM to inspect last evening, left the battery disconnected and re-installed today. Fired the car up and took a short test ride. Ran it about 20 minutes and noticed only a hint of fumes (still kinda hard to tell because the scent is in the cabin). Then I turned the air conditioner on and it blew cold air (as of yesterday before removing the RCM it did not blow cold air). And to boot, the Check Engine light was not lit, meaning no more P0410 code for now.

I don't know what to make of all this except for maybe unplugging and plugging the RCM and/or leaving the battery disconnected overnight reset something. In any case, I'm going to still have the exhaust system looked at tomorrow and ship my RCM off to Tighed for repair (did not see distinct solder cracks like in the example, but connections were not like the others).

If anyone has a theory or have experienced such as described above, would be interesting to hear.

Thanks!