Black 'stuff' where fuel lines go through body

[D911SC]

In cleaning up under my car I have come across a black tar like coating where the fuel lines and brake line go though the body to the rear. With a bit of scrubbing and grease remover it is coming off. I have seen some other pics by searching this site and it appears to be a factory coating.

Can anyone tell me if this is the case and what its purpose is? I am guessing it's to provide a barrier of some sort.

The real question is that after I have cleaned it up what would be the right product to re-apply?

Here's a borrowed pic - it shows it better than the one I took. You can see that it is also on the brake line fitting which is exactly the same as my car.

[steely]

If it's the same stuff they use on top of the strut towers, it is tar - mainly to block water. I think I read where you can use a regular sealant (silicone for example).