I discovered this the other day while driving. I don't recall ever reading a post or other topic on the boards.
Since I have the PowerMax installed I find it hard to drive on some hills. The tranny will not kick out of TQ lockup allowing the engine RPMs to come up and give me the power band I need to go up the hill smootly. I discovered that when I'm pressing the accelerator (NOT flooring it, or giving a great deal of input) and I bump the brake pedal at the same time the TQ will unlock. I have tried this under several different conditions and the TQ unlocks everytime. Now if the road is rather flat the TQ will lock back up rather quickly. So if you have been using the Tow/Haul button to get the tranny to change up try the trick above and post your findings.