What was found
AIRCRAFT EXPERIENCED A ROUGH RUNNING ENGINE ACCOMPANIED BY A LOSS OF POWER. SUSPECTING A STICKING VALVE, AN EXHAUST VALVE WIGGLE CHECK WAS PERFORMED IAW LYC SB SB388B. SINCE EXHAUST VALVE CLEARANCES WERE FOUND WITHIN LIMITS, AN INSP OF THE INTAKE VALVES WAS PERFORMED. INSP OF THE NR 2 CYLINDER INTAKE VALVE REVEALED SEVERE GOUGING AND SCORING ON VALVE STEM. MARKS WERE CONSISTENT WITH TOOL JAWS AND BELIEVED TO BE PRODUCED DURING MFG OR ASSY. CYLINDER WAS REMOVED AND REPLACED. (X)