The full kit sold on ebay just recently for £800 but I reckon that is a bargain as opposed to the norm.
http://www.ebay.co.uk/itm/330787548164? ... 1423.l2649I considered bidding myself but read a few threads that put me off. In the end you will be left with a frankenstein Porsche which no one will want to buy from you should you come to sell it. You would probably be better off selling your S4 and buying a GT. Which I may be tempted to do next year. Judging by the apparent slowness the market I would probably have to put the S4 up for sale now.