Interesting, I havn't turned my fuel up at all and the boost pressure hits 12-13 psi routinly. My engine was N/A and the turbo installed and timing changed, but no fuel delivery change. The N/A engine has less fuel than the turbo version to begin with. With the pyro, you will end up looking at it as much as the tach almost, especially in hill country.
900 is probably a safe max for an after turbo sensor.
For a while, I had a digital display (Fluke DVM plus thermocouple adapter) and it registered all the temperature peaks instantly, peaks that don't show up on the "analog" gauge, so don't drive too long at or near 1,200 deg F (900 for after turbo temp).
The Multifuel engine is conservatively rated 140 hp or so. The thing is that it can run forever at that power output, but when the power is "turned up" there will very likely be a limit to how long it can run at that higher output. You have changed the classification of the engine....