On some newer, smaller turboprops (PAC750XL) the torque gauge is measured in psi. I also belive the PC-9 is the same.
Weird as psi is not a torque unit. I don't remember exactly how it is measured, but I have a vague recollection that it is something to do with measure the force of oil being thrown off the main shaft as it spins, this being related to the torque that the engine is producing.....or something like that.