probably all in the tuning. I also have the 4"MBRP which I'm sure helps.
I really can't get mine too hot on the tow setting (80hp extra) when towing my rig/trailer which weighs about 7500#. it maxes out probably around 1250-1300*
now the hot setting is a different story. I can tow with it (if I don't care about fuel comsumption
), but only here in the midwest. it would get too hot pulling larger grades like in the mountains.
I DD with the hot tune which is around 580-590hp (about 485ish at the rear wheels)