My truck runs great except when driving up hills or with a medium load with the a/c on. If I hold a steady gas pedal and try to maintain a constant speed the truck surges and seems to lack power. At the same time torque converter lock-up acts weird, almost coming on too fast, and forcing a downshift instead of unlocking converter to maintain speed. My tire size is stock, although my trans was replaced a year ago with a g.m reman unit. Is this a possible programming issue? The truck drives way better with this trans in all aspects besides the above problem. Any help is appreciated, I am a european car tech with a snap-on modis scanner that I can use on my truck but no other info. sources that apply. Thanks