Did you guys have the same gear ratio?
What about the same egt probe/sensor/box.
I batted with a couple of different guys for months trying to figure out what was wrong with their truck and why they had high egts. We went back and forth trying to figure out everything. They kept thinking it was the turbo (but the trucks ran clean, hard, made good power and boost). I kept suggesting it was the egts probe/sensor/box and they did not believe me. One had even replaced his probe with no change.
Ended up one guy was using the wrong formula for his sensor and the other one had a bad box for this egt setup (the probe was fine, just needed the new box). Both their trucks run fine now.