From reading around the forum on this subject it seems people rave about the itg panel filter in standard airbox, with acoustic valve removed and decent cold air feeds fitted. £60 is expensive for a panel filter though, i'm sure there can't be a lot of difference between all the aftermarket panel filters aparts from what they look like and the material used....
What shop sells suitable diameter cold air feeds (preferably not online)? Also looking for a cheap silicone intake elbow without the ridges - perhaps this would smooth the airflow a bit.. although the samco and hillpower bends are also expensive for what they are.