THE ACFT MADE A FORCED LANDING AFTER THE ENGINE LOST POWER DURING TAKEOFF CLIMB. THE PILOT HAD LEANED THE MIXTURE PRIOR TO TAKEOFF. THE CHECKLIST CALLS FOR FULL RICH. WHEN THE PILOT REDUCED POWER AFTER TAKEOFF THE ENGINE STARTED DETONATING AND LOST POWER. DURING THE EMERGENCY LANDING THE LANDING GEAR COLLAPSED. DURING THE EXAMINATION OF THE ENGINE AFTER THE ACCIDENT EVIDENCE OF DETONATION AND ABNORMAL HEAT WAS FOUND. DURING A TEST RUN OF THE ENGINE CONDITIONS WERE USED TO SIMULATE THE ACCIDENT TAKEOFF. THE RESULTS WERE THE SAME. THE PILOT WAS QUERIED ABOUT THE USE OF THE MIXTURE CONTROL. HEREPEATED HIS METHODS WHICH HE SAID WAS THE WAY HE WAS TAUGHT BY A CFI WHO WAS NOT FOUND FOR COMMENT. THE PILOT NEVER MENTIONED THAT THE CHECKLIST CALLS FOR FULL RICH MIXTURE FOR THE TURBOCHARGED ENGINE. DENSITY ALTITUDE WAS ABOUT 9,300 FT.