Tow/Haul mode

[Billett]

I've seen a few threads on the tow/haul mode of a truck pcm bring converted to a race style tune instead. When i asked my tuner about this he said that the factory computer cannot support that. Can anyone shed some light on this or should i be looking for a new tuner. This is the same guy who said that he could not change the output voltage on the tech signal, when I've been told that is also possible. These guys have a great record in the Corvette community but I'm starting to wonder if they are right for my build...