So I have some rattling in my engine and I have narrowed down where it is coming from, but not sure what the part is.
The alternator under the exhaust manifold, with coupler connected and goes into...
Not sure what that is.
It is a 2011 LR2 HSE 6L-3.2L.

Thanks for the input.

 

Welcome to the forum.
The alternator is under the intake manifold. Perhaps a photo would help clarify.

 

There is no alternator under the exhaust manifold. The alternator on your vehicle is under the intake manifold, as LR2Driver stated. It is impossible to even make a guess from your description. Take a photo of what you are talking about and post it.