I've had good luck with the BMC F1 high flow filter. It's an oil based cotton filter like the K&N but comprised of higher quality materials and they don't go overboard on the oil from the factory. It's supposed to flow considerable more air than the stock paper. It is the standard filter in F1 racing. Here is the link
http://shop.store.yahoo.com/eagleday/pobmcpefi.html The cheapest price I have found is 70 bucks at eagleday and some places as high as 120. Dansk headers and cats will give some gains on their own and are relatively inexpensive compared to places like S-Car-Go or Gemballa.