I have a payne oil furnace model po8uaa048125 the problem I am having is I have my thermostat set for 78 but it will not heat past 71-72 it has been constantly running for over a day now so far I changed the filter's,oil burner primary control,the eye,nozzle,fuel pump,checked the duct work for any blocks and am lost what else to do or check

Has the burner been ignited all this time? Or is it turning off before it gets to the set temp? It would seem that 70-71 degrees would be plenty hot. I cannot imagine having a house heated any more than 70 degrees; you couldn't breathe in so much heat. You would not want it that hot in the summer. If your t-stat is turning it off it could be the anticipator. You can set that for it to cycle longer, but I would be happy with 70 degrees; you will save money because at 78 degrees that doubles or triples you energy use.