I have a 3" magnaflow cat back exhaust on mine, and near stock engine except a K&N air fiter.
My friend was telling me that i could be loosing power and gas mileage because i dont have enought air flow, he says i need to get cold air, but not many companies sell them for our year, and they are expensive....should i do this??

 

You can make your own CAI if you want. I think there is an article on the homepage. Very cheap in comparison the rip off that some companies sell.

You're not losing HP by with what you have, but you'll gain a little by adding it, and same goes with mpg.