Spits and sputters

I have had a problem with my vehicle now for a couple months when it got up to temperature and was hauling a trailer it would start missing and in reverse if you jumped into the pedal it would spit and sputter. I replaced the crank position sensor four days ago and both problems went away. I have drove it about three hundred miles and it has been fine then I get home I go to back it into the drive and its start missing again. I replaced the crank sensor once again thinking I might of got a bad one since all problems went away when I replaced it a couple days ago but this time it did not fix the problem. If I put it in forward and punch it until burn the tires, if I put it in neutral or park and chop the throttle it will go as I as it wants with no hesitation what soever as well. If I put it in reverse it idles fine and if I push the gas but keep the rpm's under 1000 it is fine, but as soon as it hits a grand its all over the map. I am completely stumped. Does anyone have any clue what might be wrong? I can work on cars no problem but I suck at troubleshooting.