Our 2002 Protege 5 just got 26 mpg.... all freeway miles, and just did some city driving and it got 23 mpg. I know, not good. I had new plugs, wires, and the injectors cleaned about 4 months ago, I'm sure my air filter is dirty, should I upgrade to a cold air intake? If so what kind, and how easy are they to install and do they come with directions? I have the Borla cat back exhaust on it and has been on there since basically new, we are original owners of the car.