you can only do this with the assumption of having already a cfw / emunand setup that is not your desired region (j for ex.)
flash = restore sysnand via your emunand backup, created from your working region changed emunand
from there,
proceed as normal with plialects guide with the files from your TARGET region
requirements:
1. cfw with current region emunand (the region that you don't like) = this must be 9.2J sysnand and 9.2j emunand (not really a must, but it is best so no more Downgrading back to 9.2 extra work)
2. 9.2U files
3. while in emunand install 9.2u via SU
4. inject your secureinfo_a (US version) thru rxtools, d9 or other methods (xorpad16 and secureinfo injectool-you have to dump emunand first for the PC solution) your choice.
5. open your titlemanager or fbi, delete titles that ends with J
6. if everything is working, dump your emunand,
7. restore/flash your emunand to your sysnand
8. you now have 9.2U SYSNAND
from here follow plialects guide on getting OTP via US version tutorial
//I know there are typos and other grammarnazi targets but I'm lazy
enjoy and have fun modding your 3ds and I hope you get it working