2003 mustang 4.6l #4 cylindar misfire
 

this code has been coming up for about a week. I swapped the injectors and coil packs to other cylibndars and #4 keeps coming up. Any ideas?

If you can try making sure you have 12 volts to the #4 injector with the key on. Then switch the meter or test lite and confirm you are getting a ground signal from the PCM when the engine is either cranking or running. If both of those are present then you might remove that side valve cover and look for a broken valve spring on that cylinder. You did check the plug, right?
That should help answer where the problem lies. Let us know what you find, Thanks.