The mechanic stated that he reinstalled the right-side attitude indicator on October 11th and checked its and the vacuum system's operation. He reported that he was satisfied with the operation of both and that he removed the placard for the attitude indicator. The mechanic reported that he informed the pilot of the work that had been done and told him to monitor the vacuum gage reading on his next flight to see if the lower than usual reading he had reported earlier had been corrected by reinstalling the overhauled attitude indicator. The mechanic stated that the pilot did not inform him if the lower than usual vacuum gage reading had been corrected by the reinstallation of the overhauled attitude indicator.