Could you tell me the story of Boss Dharamsee's visit to Shirdi and the miracle with the grapes?

Certainly. As recounted in Chapter 35, Boss Dharamsee visited Shirdi with a great deal of skepticism. When Kaka offered grapes to Sai Baba, Baba began distributing them. Dharamsee disliked this particular variety of grapes because they had seeds and were unwashed. He was troubled, thinking that if Baba were a true saint, he would know his dislike. Seeing his hesitation, Baba insisted he eat them. When Dharamsee finally obeyed and put the grapes in his mouth, he was astonished to find they were completely seedless. In contrast, another devotee, Tarkhad, confirmed his own grapes still had seeds. This personal miracle completely dissolved Dharamsee's doubt, and a deep love for Sai was born in his heart.