Our Route Performance manual contains an extra page for each aerodrome with reduced torque settings (and V1 VR V2 speeds) for a given T.O.M for use in prevailing conditions where reduced power would be prudent. Aircraft is Saab 340B,
GE CT7-9B Engines, lowest figure i have seen in it is 86%. Max torque is obviously 100% however there is an extra 7% availiable from the engine in the single engine case. However due to some of the aerodromes on the network there are a lot of occasions where reduced power is not an option due RWY length/surface/terrain/obstacle performance issues.