It's in the pipe just below the OS headlight, IIRC a torx bolt holding it in TX25 or TX30 (possibly)
Looks like this
http://j-w-racing.co.uk/product.php/..._ford_focus_st
As long as ignition is off it's fine to disconnect it.
Last edited by GVK.; Oct 26, 2013 at 07:22 PM.