Yah, the DT466E is castrated from the factory. There is more than enough reserve capacity built into the DT. I don't know why they set them so low, because driving foot to the floor all the time plus the high operating temp only wears things out. I used to roll the rental trucks for work and they were geared wrong, especially with the 545 Allison auto. The overdrive/lockup style auto was much nicer (I think it was a MD3060).
I'm a power junky anyways, and as far as I'm concerned 350hp should be a good starting point with 850 ft/lbs minimum for a motor that big. ;p
As long as the computer can be hacked, I'd like to see what a set of Extrude Honed nozzles, twins and some of the PSD tricks can do to one of these engines. I believe there is a power box available, but doesn't have enough kick.