In looking over some of the specs for each programmer, some state HP/Torque gains at the rear wheels, and some offer HP/Torque gains at the flywheel. There are obvious power losses going from the motor to the rear wheels. There should be an industry standard for all of the specs. It seems that owners who state better MPG gains with Hypertech and Superchip, the programmers have slightly less torque gains associated with the HP gains. Compared to the Predator and PPE that don't get major HP gains, and there numbers have slightly higher HP and Torque numbers. I'll go out on a limb and state the MPG gains are more closely related to torque numbers. Examples:
Predator Hypertech Superchip PPE Bully Dog
45 / 100 48 / 87 65 / 114 70 / 140 48/??
65 / 140 70 / 131 86 / 151 160/290 69/150
85 / 170 95 / 175 119/206 225/390 138/298
120/250 (not sure)
In short, the more mellow the programmer, the better the MPG gains. Anyone with more expertise, please jump in! I'm only a rookie.