As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE FLIGHT THE AIRFRAME DEVELOPED A LATERAL VIBRATION WHICH INCREASED IN DIRECT PROPORTION TO THE INCREASE OF AIRSPEED. MAINTENANCE REPLACED TWO BIFILAR BUMPERS AND THE MOUNTING CLAMPS (PN 700006-2) AND (PN 6438B-103) ON ONE ALTITUDE INDICATOR AND ONE HSI.