Don't know the answer, but my Autometer Pyro gauge 0-1600* has been on for over year and a half. I have had a HOT Juice/Attitude pyro sensor pre-turbo about an inch and a half from the Autometer pryo sensor. They always were within 25* or so. Same after I switched to the TST PowerMaxCR, the TST pyro sensor replaced the Juice pyro sensor and it too is very close to the Autometer gauge at any reading.
Just trying to say that the Autometer and Isspro should give numbers very close to the same. One certainly needs calibration, wiring check, etc. I guess I am predudice, but I would lean toward the Autometer readings. My 600 with an EZ could push 1450* if I got on it hard on higher level.