Motors air filter - insurance?

After taking the remains of the old muffler off my truck and replacing it with a glasspack there was about a 2mpg increase from the winter with the stock muffler to when I put on the glasspack. I probably drive it about the same and still take the same route to work but it does make a difference.

 

The only performance increase you will get from putting in a cold air intake is if the new setup weighs a fiew pounds less meaning less strain on the engine.

Now the negative. Most air intakes act as a vacuum for puddles of water when configured as designed or the shorter cheaper ones put hot air in your engine robing power.

So in any case the gain is non existent. If your racing your car then chances are your motor has some serious tuning and possibly dosent have an air filter at all and just an open hood and mosquito net over the intake manifold.