HELP: cool air intake filter kits '08 Ext?

what cool air intake filter kit work on the 2008 cadillac ext, and does it really add horsepower and mpg.

GM PERFORMACE PARTS sell one now. I would not expect a large increase in either area, but it looks good compared to stock.

I was told this would work and your MPG would go up if you could keep your foot out of it.(Great sound)
 
http://www.procarparts.com/product_info.php?products_id=2323&osCsid=47a0739e3b1485a2bf1005624bb4cfbf