A cold air intake or induction system includes intake piping, the theory being that you should have the filter, which is usually cone-shaped, located somewhere it may draw in cold air, usually in front of the bumper or somewhere close-to air circulation away from engine heat. An aftermarket air filter with no induction piping can be installed to replace your factory air-box which sits inside your engine bay. Or there is the another form, the drop in filter, that is manufactured to out flow your factory filter with out causing any of the side effects generally associated with aftermarket CAI systems and rests inside the air-box, in the spot of the typical paper edition. Do these performance air filters work? From my own personal experience owning everything from a low powered, essentially stock car I would say most certainly YES! A friend had told him that you could get an extra 40hp from the engine with performance spark plugs and a K&N filter. Although I do believe you almost always get what you pay for, 40hp sure did sound appealing, so I gave it a shot and along with a re-tune I am extremely happy overall. Keep your projects goal in mind, it was not until I upgraded my turbo that I decided to ALSO upgrade to a larger diameter cold air intake system. Depending on your power goals a drop in air filter from cosworth or hks may suit you just fine. Always feel free to call us and ask for advice, we wont steer you wrong!