The short version is that the audio and video outputs have both been upgraded to the best quality possible, and the power regulation section has been completely rebuilt, a power LED has been added, and it is now able to play both USA and JPN carts (but not PAL). I'll put together information to update the original post with more details.
Edit: Ok, I've edited the original post with better descriptions of the mods, including links with more information (no auction terms were modified).
Edited: 04/10/2019
at 08:03 PM
by qwertymodo