How many foot pounds needed to turn mag 5.9?

From my harbor freight torque wrench and my inexperience i very between 25-31 pounds

Is that with a missing piston? Either way, that does seem high. Try breaking each main cap loose and try it. Retighten if it doesn't make a difference then go to the next one. If you do all the mains with no difference, do the same with the rods one at a time.