when i start up and run the lincoln; i need to keep my foot on the gas to keep it running, or it will surge up and down rpms, and if i put it in gear it surges up and down still cant figure it out plaesse help its a 5.0 engine

 

My Lincoln did the same thing, you may have some vacuum line problems, there is a vacuum line under the manifold that may have split, mine was split and after i replaced it, it ran fine.