In the Fiesta RS Turbo, what line is plugged here? In my car there is nothing - it is blanked out with a rubber cap, any ideas why? This is a vacuum port as far as I can tell, correct?

 

Seems that I keep asking stupid questions. The port is blanked from factory, what confused me was seeing so many cars with a line attached to it in pictures. Seems it usually serves for plugging there either a boost gauge or a dump valve.

Doh.

 

That's the coolant overflow tank alright. The lines typically go to the radiator and engine block. But hey, don't just take my word for it - always best to consult your car's manual or a pro if you're not 100% sure. Better safe than sorry when it comes to car stuff, right?