Great timing for me on this topic.
I got a BDGT last month and have been playing with it looking for optimum setting.
In my desire to understand what is happening, I got a bluetooth OBDII reader and put the Torque app on my phone so I can log sensor data to see if I can figure out what is changing beyond seat of the pants sensors!
I haven't learned anything yet, but have a bunch of data..
When I ran the Extreme tune, the difference was incredible. I had the 2* advance on my timing also but found the throttle was too sensitive. The truck was twitchy. Fun as heck, but twitchy. Better without the 2* timing.
Now I am running "regular tune, WOT disabled, 2*, and speed limit at 151mph, but throttle sensitivity at stock. I'm gathering data and will compare to data collected when truck was stock (no DGT). The difference is subtle.
Then I'll change the tune settings and keep collecting data. I kinda doubt I'll figure it out but who knows..I like data and have the time.
My concern is that the tuner really only changes the throttle sensitivity and as such, creates the illusion of more horsepower.
If anyone has any insight into differences between tunes chime in. I'd love to know more about what this thing is doing.