Manafold full of poo

[JayM1969]

So while doing the Mr muscle clean today I had the EGR off, I had cleaned it 9 months ago and to be honest it just required a quick wipe.
However, I took a look down the, forgive me if I am wrong, the intake manifold and its encrusted with black poo, to the point where it must only have a third of its bore usable.
I have a few questions...

1. Do I leave it and hope that it will just go away ???
2. If I am to clean it, is it best to remove it ?
3. If I remove it, is it easy enough and do I need to purchase any new gaskets ?
4. Has any one done this, will the car benefit from it ?

Thanks in advance Jay.