The Performance and Hot curves inhibit the 3->4 for TP at 50% and up...
( Performance = Tow/Haul switch position, Hot = overheating mode )
but the Normal and Cruise curves allow this shift.
I see now. Thanks!
I am in the same boat, this thread has been a wealth of knowledge. I'm building a 5.3 turbo Mustang with a 75mm turbo and a PSI harness.