Welcome on board.
The Diverter Valve you'll want is the Revision G, P/N
06H 145 710 G, £35 from your local dealers.
Leave the OEM filter in place, get the map put on and see what you think. You'll be VERY happy by the performance gain as it is. An intake can bring some lag to low down torque so unless your always running your car to high revs stick with the OEM filter, you'll not get any gain adding an aftermarket panel filter (such as a Pipercross or ITG) either.
If/when you go stage 2, add a CAI then along with a decent TBE system, all IMO though.
Check/change your cam follower and do the same with your PCV before getting the map, good precautionary measures.