Not sure how others feel, but the 350 2013 KTM just doesn't feel like a 450 class bike with the 250 sounds. So here is the 450 sounds applied to that bike. JLV did give me permission to upload this.
How to make it work?
Download the file
Move the saf into your personal folder
Restart or start your game.
How to uninstall the new sound update?
Delete the file called "sxf350v2013_sound_replacement_450f_sounds.saf" and restart your game.