Honestly, easiest way forward is to flash the new speaker fix 6.1.3 ROM. Unzip and run flash-all.bat. Flashes us bands as well as part of the package.
After, you can use snwriter to change the IMEI (confirmed working). Then flash just AIV’s kosher super with fastboot.
fastboot erase super
fastboot flash super /path/to/super.img
I know it sounds like a lot, you can go another way if you want, I just think this is the easiest because that package includes the bands…