How to change the operating point of the SPT100 Thruster

I’m currently using SPIS to model the SPT100 thruster’s plume but I would like to change its specific impulse, power and thrust and I was wondering if anyone could help me. I’ve tried to randomly change temperature, Mach number and current of the species emitted by the thruster and I saw that those parameters change so I was looking for the coherent way to do so.
I appreciate any help!
Thank you,