I imagine if you tap into the wires the TT is hooked up to...the gauge would stay on as long as the turbo timer is on
But it would work...
You have a lot of options actually. A very common tap is the power/ground to the clock in the clock pod, especially since its easy to pop out and get to.
I actually used the accessory outlet because it has clear and discernible positive and negative wires and turns on and off with the car= perfect. Its also very easy to get to.