A heading hold gyro needs revo disabled (INH) a normal rate gyro needs some revo mixing.

As you increase power the torque on the drive system increases requiring more tail rotor pitch to keep the helicopters nose pointed in the right direction. Thats all revo does, increase tail rotor pitch as you incrase power and decrases it as you back off.

With a Heading Hold gyro it will cause all sorts of mischief and needs turned off.

What gyro are you running?