[Backtobasics]

There is a lot of untapped potential in the average diesel truck, as the OEMs do not know what the person is going to do with it. There is such a large range -- Fully loaded all the time (lawn and landscape), around town combo use, or unloaded high performance enthusiast. As such, they can't the more aggressive tune, as the guy who works it hard loaded, would kill it. The diesel programmer market is huge, as they can give huge power and torque gains for moderate cost, yet almost all have multiple levels, and they highly discourage towing and loaded use in the more aggressive settings for the engine damage reason.
This is also the reason that these vehicle respond so favorably to the other 2 common modifications, air intake, and exhaust. The engine is not restricted by throttle blade such as gas motor, so unrestricted air intake has benefits, and low restriction exhaust compliments the turbo, which likes reduced back pressure.
I wish I could trade my moderately lowered 2wd gas truck for the same in a diesel, I bet I could go from the 15 I get now to 25+.