[Battle] Adding special and physical split of the 4th gen games

I was wondering if anyone has any idea of how to apply the special/physical split, introduced in gen 4.

I don't really want to have to patch the rom, i want to do it manually to be sure i know what changes are done to the rom.

I forgot to mention that i'm hacking an emerald rom.

Doesnt's version of the split (the only one that works outside of the Emerald battle engine upgrade) was made by porting a Japanese patch to an English copy of the game, so there's no proper "source" available for it. If you really wanted to see exactly which bytes it changes, you could apply the patch to a ROM and then compare it to an unpatched ROM using a hex editor, which will show you the modified bytes.

You could also read which bytes the patch changes using this information on the ips file format.