FIPK kit
 

Is it true that K&N FIPK kits allow a 15 HP gain?

I highly doubt it adds 15 HP. I was looking into the FIPK as well but the kit just doesnt seem real popular with Stangs. I browse a lot of different mustang message boards and have yet to come across one person who has a FIPK kit installed; there must be a good reason for it. For now im just stickin to the stock setup with a K @ N filter(air silencer removed). Anyhow, the C @ L MAF seems to be real popular.