As the power lever is increased this moves the metering computing section in the FCU, this now allows extra fuel (Wf} which in turns increases N1 and as such ITT. This increase follows till the computing section reaches the position set by the power lever. Tq there fore follows to increase. However Tq can be adjusted via the Prop Gov via the prop lever.
The prop is set via the Flight angle stting on twins and via the prop shop on most singles, this setting WILL NOT STOP an over Torque.
The Tq limiter only drops Px air px which inturns resets the FCU computer and takes fuel away from the Fcu and there fore a decrease in Wf and slows the engine down.
The engines performance really all comes down to the condition of the air gap at the compressor turbine. This is what you damage when you start when your voltage is below what it should be and you hot start.
And remember in a PT6 the engine is in two parts the compressor section and the power section and its air coupled between the two sections,
this is just a basic run down of the PT6