What is making my truck idle rough?

I have an 03 Ford F-150 and starting about a year ago it was starting to idle rough while it was in park but now it does it when simply not moving. The rpm keeps jumping up and down and the truck vibrates real bad almost like it s trying to fight to stay running. If I let it sit like that eventually the lights dim and it does almost die. I have had plugs and coils changed 6 months ago but could it be another issue? Battery or injectors? Any help would be great thanks!

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