WHILE CLIMBING THROUGH 6000 FEET THERE WAS AN UNCOMMANDED REDUCTION OF POWER ON THE RIGHT ENGINE, ACCOMPANIED BY A WARNING OF THE THRUST REVERSER BECOMING UNLOCKED. THE ENGINE WAS SHUTDOWN AND THE AIRPLANE RETURNED FOR LANDING. A READOUT OF THE DFDR DISCLOSED THE THRUST REVERSER WAS NEVER UNLOCKED. THE INVESTIGATION DISCLOSED THAT THE RESTRICTOR PLACED IN THE BLEED AIR LINE USED TO HEAT THE REVERSER COMPONENTS WAS TOO LARGE AND THESE COMPONENTS HAD BEEN EXPOSED TO EXCESSIVE HEAT. ELECTRICAL WINDINGS HAD FAILED AND A FALSE SIGNAL OF AN INFLIGHT THRUST REVERSER UNLOCK CAUSED THE POWER TO BE REDUCED ON THE ENGINE. THE ENGINE WAS ORIGINALLY MANUFACTURED BY PRATT & WHITNEY AS A PW4460 AND THEN REBUILT AS A PW4152, AT WHICH TIME THE REVERSER COMPONENTS MANUFACTURED BY ROHR WERE ADDED. THE JOB WAS DESCRIBED AS A 'RUSH JOB,' AND ROHR SENT TWO MECHANICS TO ASSIST PRATT & WHITNEY IN THE REBUILD.