Jeff, do you know about what mass flow rate each torque/power curve corresponds to? I was just looking at the compressor maps and it looks like at the pressure ratio of 3.0 (about 1.9 bar boost), the GTX won't start to show gains until about 45lbs/min with those gains getting big at 55 lbs/min. And of course, the regular GT dies around there whereas the GTX will push to ~65lbs/min.
Did you have to change any of the tune? Any timing adjustments or anything like that?
One last question, any plans to do the GTX3071? I imagine it will make similar power as the GT3076, but the on/off transient boost response should be better. Of course, only way to check that is on the street.