I'm a new poster but have enjoyed ready this Forum in the past and have gotten a lot a valuable information off of it. My 89 4.0 has a small hose fitting on the intake manifold that is covered by a 1" long rubber plug. I've always noticed it but never paid much attention to it until this week when I discovered it could be removed and found the fitting underneath. Does anyone know why this is there? Was it meant for some sort of emission device that my vehicle wasn't supplied with? Thanks!