Just cut the perforated metal off of the filter it will then flow all you need, NO COST. I vented the airbox to let plenty of air in, this works well with my decat & bigger exhaust,Is there a high flow air filter option for the stock air box? I don’t seem to see where K&N makes anything for it.
I used to belong to a VW tdi forum where they frequently had people ask about fitting 'high flow" air filters. A few of the members came back with evidence that the factory paper filter can flow more air than the engine can use. Personally I think K&N and their ilk are a waste of money, and could potentially lead to top end damage, but to each their own. No doubt K&N will produce one at some point.