Beyond a remap I think you are talking fairly big bucks for any serious modifications - probably not worth it. I would advise agains a K&N open type filter (look here http://uk-mkivs.net/forums/thread/98450.aspx ). Because V5's are comparatively rare I gather that cams etc would need to be custom as there is not a mass market. I'm sticking just with the remap as I've heard most other things are a bit of a risk unless you have thousands to spend. Beyond engine/tuning mods the Milltek may add a few more bhp but I would be surprised if it adds much more than about 5 tbh.