http://secure.50resto.com/product1.cfm?SID=1&Product_ID=1849&Category_ID=906
I trust 50resto.com. I bought several parts from them already.
How to install them.
http://www.mustangworld.com/ourpics/fcar/cobralights.htm
I heard the K&N one works okay too. But the stock air tube with a removed or cut snorkel/silencer/whatever works almost the same if not better than a cheap CAI like BBK or Mac.
I was told the same thing when I got my exhaust put on. The computer has to relearn. It takes a few cycles to adjust. Just drive it and you'll be fine. I noticed no loss of power down low. :shrug: