I just started playing this mod a few days ago, and so far have been VERY pleased (Yoshimo is my favorite in game recruitable npc in BG2, and along with Aerie, Jaheira, Keldorn, and Valygar [badly underwritten in game], is one of the few non mod npcs who I regularly recruit).
When I first played the mod, I started a new game of 'classic' BG2 from the beginning. I didn't know that Ilmater's messenger and Yoshimo were supposed to spawn at the exit to the pocket plane after completion of the first reckoning/trial. After defeating Illasera, Grommir, Yaga Shura, and Draconis, Yoshi was nowhere