What was found
(CAN) ON APPROACH, THE CREW NOTED THAT THE HSI WAS STICKING ON PREVIOUS HEADINGS IN BOTH SLAVE & FREE MODES. THE ACFT WAS SELECTED TO GPS RNAV FOR THE REMAINDER OF THE APPROACH & THE ACFT LANDED WITHOUT DIFFICULTY. IT WAS FOUND TO BE THE GYRO AS THE FAULT, IT ONLY HAD 60 HOURS ON IT SINCE BEING INSTALLED.