Well anytime a tuner says you can only tow with 40 hp tells me they are only dumping fuel in the motor and not adjusting anything else.
Not exactly. Altitude, weight, gearing, etc all play a role in how each power setting will run, regardless of tuner brand. There are times when even the best programming needs to be turned down due to EGT's rising too high. The more power you add, the more fuel you are getting, and energy = heat. Besides, every single tuner manufacturer is going to stress safety first. Jody has live tuned my truck here in Colorado, and adjusted timing, fuel tables, shifting, ICP, etc. It's much harder now to get EGT's over the redline, but it's still possible in the higher HP tunes.
You can tow in the race tunes all day long, if EGT's stay below redline. When you hit mountains, that high performance program will run too hot. You have to cut back on fueling in order to keep the temperatures down. EGT's that are sustained too high for too long will start to melt pistons.
Right now with my current setup I can tow (and have done this quite a few times) in the 80 hp tune right up Eisenhower pass and several others. However I have a few other supporting mods that help me do this. Even with identical programming on a truck with a stock turbo and stock intercooler, they can't do that. I suppose I could try to make it up in the extreme race tune, but I would have to slow down a lot, and downshift and keep RPM's high enough to supply enough air to match the fueling. Why tow uphill at 50 mph when I can drop a setting, get lower EGT's, and run up a mountain grade at 70 mph?