Some clarification, so this doesn't become a you're driving too fast thread -
I could pull it (my 08 Tahoe) 75 up and over with no problems at 3/4 throttle because it had a proper downshift, plenty of power, no problems, hardly felt it was there.
This Yukon I was going 40 mph pedal to the floor (in tow/haul mode) in the right hand lane with flashers on while it dropped below 2k rpm's before downshifting. On the way back I did it in Manual and didn't have the downshifting issues because I was controlling it, but it did feel like I was pushing it a bit.
A local shop suggests a "super chip flashpaq" to reprogram the computer when I am towing. He thinks I am programed to be in what he called "economy mode". It sounds like a good idea especially when I am done towing I can easily reprogram it back to "economy mode" as a grocery getter. Any thoughts on this idea?