Can you explain the significance of Vitthal in the lives of Sai Baba's devotees based on the provided texts?

Based on the narratives in Chapter 4, Vitthal of Pandharpur holds significant importance as a focal point for devotion and faith, which Sai Baba often used to guide his followers. For instance, Baba promised Das Ganu that the form of Vitthal would appear at the end of a Name-week (Saptah) if the devotee was full of faith. In another account, Kakasaheb Dixit had a vision of Vitthal during meditation, which Baba immediately confirmed by asking, "Vitthal Patil had come, right?" This vision was further validated when a picture seller arrived with an exact replica of the Vitthal he had seen. Furthermore, Baba corrected Bhagwantrao Kshirsagar for neglecting the worship of his family's Vitthal idol, demonstrating Baba's own respect for this form of worship and its importance in a devotee's life.