Our Metro 11 has an ITT limit of 885 degrees C with the RPM back at 96%. That means maximum power available is climb power with these reduced revs.
Compare this with Max take off power (5 mins) 100% RPM, max ITT 923 degrees & torque 2363 ft lbs.
or max continuous power at 100% RPM maximum of ITT 923 degrees & torque 2206 ft lbs.
So with lower than 100% available RPM you will cook the turbines at lower temps with corresponding lower available power.
Put it another way the slower the airflow through the turbine engine the less power is available.
I hope this helps