This is a hack of Pokémon SoulSilver which changes the teams for the Johto Gym Leaders and Elite 4 to give them more Johto Pokémon (or place more emphasis on Kanto Pokémon, for the two Kanto-based Elite 4 Members, Lance notwithstanding), and a slight change to Red, giving him the Espeon he originally had in GSC. There's some mild level tweaks and these trainers generally have at least one more Pokémon. The post-game trainers and rematches, Red aside, have not been touched.
This is not considered a difficulty hack as the intent is NOT to make the games more difficult, just to change up the teams a bit.
If you're having trouble getting the romhack to run properly, the DSPRE suggested version should work.
Database match: Pokemon - SoulSilver Version (USA)
Database: No-Intro: DS (all) (v. 20210227-111036)
File/ROM SHA-1: F8DC38EA20C17541A43B58C5E6D18C1732C7E582
File/ROM CRC32: D8EA6090