Whether they are still available or not and current prices may differ..........
http://imdomino.imgroup.co.uk/IMGGB/WWW/Subaru_Accessories.nsf/WebInternetAccessories/1A4DFF82135584068025758300575FBA?Opendocument
Different to that shown by SJAR - just a splash guard
http://imdomino.imgroup.co.uk/IMGGB/WWW/Subaru_Accessories.nsf/WebInternetAccessories/3707A7A65460763080257582005183A5?Opendocument
They seem to be available from Japanparts
https://www.japanparts.com/parts/detail/45324
https://www.japanparts.com/parts/detail/40017
Seal kit is 26697AG000
Available from ICP and Scoobyworx
Seal kit is also fitted to some Legacy models as well (but only the seal kit - used for double piston front caliper))
http://www.scoobyworx.com/genuine-1-pot-impreza--legacy-rear-seal-kit-26697ag000-12065-p.asp
https://www.importcarparts.co.uk/parts-info?id=13105&cat=0&sub=0&sec=0&var=0&dc=0&gen=&searchKey=&searchPart=
Suitable donor vehicle being broken on ebay
http://www.ebay.co.uk/itm/2008-SUBARU-IMPREZA-RX-2-0-5-DR-MANUAL-BREAKING-1-DOOR-HINGE-BOLT-BREAKING-/282212075538?hash=item41b5268812:g:QcAAAOSwBahVVHRR
and
http://www.ebay.co.uk/itm/2008-SUBARU-IMPREZA-2-5-WRX-1-DOOR-HINGE-BOLT-BREAKING-SPARES-/282011513903?hash=item41a932342f:g:PB4AAOSwcu5URoJ5
Plus possible replacement LED brake light
http://www.ebay.co.uk/itm/CHMSL-Universal-Red-LED-12V-Car-High-Mount-Third-3RD-Brake-Stop-Tail-Light-Lamp-/111986073194?fits=Car+Make%3ASubaru|Model%3AImpreza|Cars+Year%3A2008&epid=1477356016&hash=item1a12e3de6a:g:sW0AAOSwubRXKF0H
There are two connections the larger is the return from the dump valve( pipe item 5 below) , the smaller the connection to the PCV valve (pipe item 2 below)
Belo just to show the turbo inlet pipe connections
GRB is a JDM 2.0L STi Widebody Hatch (G12 model code)
GVB is a JDM 2.0L STi Widebody Saloon (G12 model code)
GRF is a Uk/Euro 2.5L STi Widebody Hatch (G22 model code)*
GVF is a Uk/Euro 2.5L STi Widebody Saloon (G22 model code)*
GHE is a UK/Euro 2.5L WRX Narrow body Hatch (G12 model code)
*All JDM Hatches and Saloons come under the G12 model code whereas for the Rest of the World there is a distinction.
As used on.........
and aparently the XV