2003 Dodge 2500 Hemi towing improvement advice

Thanks for the advice. The pedal is to the floor although I let up when it shifts into 1st gear cause it will push 6000 rpm. The truck is not in need of any Maintenance it is very well maintained. I do keep track of the mileage every tank gets very consistent 11.5 mpg in town, Freeway 15-16, Towing gets 8-9 mpg. I don't know if it's a gearing problem or what but it feels like 9000 lbs not 5500 lbs.