2002 Ford Taurus W/intermitant misfire codes

I keep getting a P0302 and a P0316 on my 2002 Ford Taurus. It is showing cylinder 2 misfiring in the first 1000 rpm's. This did not happen until the thermostat stuck and it overheated. I fixed the thermostat and after that I kept getting the misfire code for cylinder 2. I changed the plugs and wires. The plug in cylinder 2 was completely destroyed. the ceramic electrode was just gone. After I changed the plug it ran fine for a couple of days and then the damn light again. checked the plug and it was in perfect shape. Don't think it's a head gasket because it does not leak any water, no water in the oil or coming out th etail pipe. If I reset the computer the car will run perfecct (good as new) for about 2 days and then the light comes on and blinks (Makes it run like crap, I think the computer is shutting off fuel to an injector as some kind of safety) After a minute or so the light is on but not blinking and it still runs bad. I found a technical service bulletin that addressed those very codes and it suggested to have the computer reprogrammed with new threshholds. I guess the emission limits were too narrow or something. that may not be the problem though. it just seems very supsicious that i did not have this problem until after it overheated. I am unsure how to proceed now as I can not afford to take it to a ford dealer where things are very expensive. Thanks in advance.

if those are the codes and you have the DOHC then ck the egr valve to see if it is stuck or if the motor for the valve is working