Can you tell me the story of Boss Dharamsee and the miracle of the grapes in Shirdi?

Certainly. As recounted in Chapter 35, a devotee named Kaka brought grapes with seeds as an offering to Sai Baba. Boss Dharamsee, who was also present, disliked this variety and was hesitant to eat them, especially since they were unwashed. He harbored doubts in his mind, wondering why a true saint would force something upon him that he disliked. Seeing his hesitation, Baba insisted, 'Throw them in and eat.' When Dharamsee obeyed and put the grapes in his mouth, he was astonished to find they were completely seedless. This experience amazed him, and he realized the profound power of the saint. Chapter 35 further notes that when he asked another devotee, Tarkhad, his grapes still had seeds, showing the miracle was meant specifically for him.