AST removal and Rad caps?

[leeroy_25]

I was looking at some pictures of a car earlier running a single turbo setup and I noticed that they appear to have removed the AST from the water system and had a pipe running direct to the water filler bottle down infront of the wheel.
Is this a common setup and if so what are the pro\'s and con\'s for it.

Also can you run a traditional style sprung rad cap on a 13B motor on the ally header tank bit attached to the engine or will this not seal properly or just bugger up the way it works?

Thank you
Lee