I get 12-14 pulling my 34' Toy hauler, about 16-17 in town and around 20 on the highway.. All these are if I keep it at or under the speed limit. If i drive normal (for me) everywhere, i get 10 with the camper, 14 in town and 18 on the highway. All hand calc'd.
basic mods, pcv, egr, air box mod, transgo jr, 4" straight, with a 225 tune. I have no idea what I get at the track with the bigger tune.