I apologize for posting again. I'm sure i'm beginning to get on some peoples nerves now but I cant seem to find all the information i need by searching or googling.

On engine strip down, my valley cover has a fitting on the rear of it, and a rubber tube that runs down to the back of the block.  

I beleive like this  

I take it this is whats known as a road draft tube? what is it purpose? Is it a breathing system? I see no other similar devices on my engine from the crank case etc. Is this sufficient? Should there be any others?

Is it worth fitting any other breathers anywhere such as the valve covers?

Regards,

Jamie