Stacking does not work on these trucks like it does on the Cummins engines.
Try getting a DP-Tuner (DP-TUner.com) Tony Wildman (totaldieselperformance.com), Diesel Innovations Chip, (dieselinnovations.com) just to name a few of the known programmers here.
For the 7.3s its best to go with a chip instead of a programmer