Good start. With sitting for that long there are lots of possibilities.Draining the tank is a good step. Though you put 5 gallons in there, the fuel that was in there was bad. Sounds like your getting fuel at first, but once it warms up, anything is possible. Thermostat could be sticking and once it warms up it could be throwing the sensors into limp mode. Hows the oil pressure ?Its a 1993 2.8 5 speed 2wd standard cab short box. With 89xxx miles. I put marvel mystery oil in all the cylinders and let it soak for a while. I also added sea foam to the tank and 5 fresh gallons. It has a new coil and ignition module. I think I'm going to start fresh and put a new fuel pump & filter. Completely drain the tank. And change the thermostat.