1) K&N Air Filter - Cheap, and worth every penny - ~$30
2) Synthetic Oil (Amsoil or Mobil 1, take your pick. I use Amsoil) - ~$ depends
3) Find out how much air your tires can take, and fill them up a few pounds shy of the max
You'll get a few extra HP from the filter, better gas milage (from filter, tires, oil), and better steering ability from the added air in the tires.
2) Synthetic Oil (Amsoil or Mobil 1, take your pick. I use Amsoil) - ~$ depends
3) Find out how much air your tires can take, and fill them up a few pounds shy of the max
You'll get a few extra HP from the filter, better gas milage (from filter, tires, oil), and better steering ability from the added air in the tires.