Ok I don't know if this qualifies as a mod,,,but...
have you discovered a 3 month old cheeseburger under your seat?
does your car ever get that "not-so-fresh" feeling?
do you eat a lot of beans?
do you think air freshners look tacky, and scream to the world "hey!!! look at me!!! I smell bad!!!"
...then this mod is for you.
it smells great, and its 100% invisible and undetectable. not even your mechanic will know.
first of all, you have to know that there's an air filter behind your glove box that filters all the air that goes to your vents. Even if you didn't get this option from the factory, the spot where the filter goes is there, and you can buy the filter from subaruparts for about $30. The filter works great by the way...I put in a white one every 20k miles and pull out a BLACK one.
So here's the mod:
when you install/replace your air filter. Spray the filter with whatever smell you like before inserting the filter. You may have to re-apply every once in a while. Second, you can place a dryer sheet on top of the filter before you slide it in. The most complicated version of this mod is to take TWO unsented dryer sheets, and place between them the sented substance of your choice, and staple around the outside of the dryer sheets, then place this assembly on top of the filter.
so there you are. now your car can smell pretty instead of like a sweaty nutsack, and no one has to know your diet consists mainly of broccoli, beans and sour milk.