THE PILOT HAD EXPERIENCED A POWER LOSS UPON POWER REAPPLICATION FOLLOWING IDLE OPERATION SUBSEQUENT TO LANDING ON SEVERAL PREVIOUS OCCASIONS. AFTER DISCUSSING THE SYMPTOMS WITH A MECHANIC, AND DECIDING THAT THE FUEL CONTROL SYSTEM REQUIRED ADJUSTMENT, THE PILOT INITIATED A FLIGHT TO THE MECHANIC'S FACILITY TO CARRY OUT THE INTENDED MAINTENANCE WORK. SHORTLY AFTER DEPARTING FOR THE MECHANIC'S AIRSTRIP, AND AT THE COMPLETION OF A 360 DEGREE SPIRALLING DESCENT TO LOSE ALTITUDE PRIOR TO LANDING, THE PILOT REAPPLIED POWER, EXPERIENCED A SURGE AND THEN LOST ENGINE POWER. HE EXECUTED A FORCED LANDING ON SOFT TERRAIN DURING WHICH THE LEFT MAIN GEAR SEPARATED AFTER THE GEAR BEGAN TO DIG IN DURING THE LANDING ROLL. THE FUEL CONTROL METERING UNIT HAD BEEN REPAIRED IN APRIL OF 1991 PRIOR TO THE AIRCRAFT'S SALE AND RELOCATION FROM NEW MEXICO TO MONTANA IN NOVEMBER 1991.