No, because you can't do that with stock injectors at altitude on a 7% grade at 1800 rpms in OD either. Because it ALWAYS downshifts or continues to slow down. You cannot maintain speed on a stock calibration because there isn't enough power, and if you want more power... you MUST downshift.Were you pulling those heavy loads up a 7% grade at 1800rpms in OD while keeping egts under 1100? Dont forget about that part.
My truck would also downshift, just like the stock calibration.
I would bet you can tow with ANY turbo/injector combo. But you are going to have to change your driving style and work a lot on tuning.
Tuning yes. Driving style... no.
Learn how these trucks drive before you try and talk smack to someone else. Obviously you've never towed heavy at altitude... stock or not.