Cold Air Intake
What is a cold air intake (CAI)?
Basically, a cold air intake replaces the stock intake track forward of the throttle body with less restrictive parts.  A common theme of aftermarket cold air intake kits is they relocate the air filter out of the engine bay or they replace the stock air filter box with a filter box that is less restrictive.
How Does a CAI Work?
There are two ways to increase the power at the drive wheels:  Make more power from the engine or free up parasitic loss of the power already produced.
The CAI helps the engine make more power by reducing the restrictions built into the stock intake track and it allows the engine to breathe cooler air.  Cold air contains more oxygen and therefore results in "more" air into the combustion chamber. 

A common theme in making more power from any engine is "more air in, more efficient burn, more air out = MORE POWER." This principle will be the basis for EVERY power making modification to my Cobra.
Going the Homemade Route
There are many aftermarket companies that sell CAI's.  These pieces are usually high quality but come at a price.  The majority run in the neighborhood of $150.00+.  The average CAI will increase power in the neighborhood of 5 to 10 horsepower.  Doing the math, that comes out to $15 per horsepower.  That ratio isn't bad, considering most cat-back performance exhaust systems cost over $300.00 and result in the same or less power gains than a CAI. 

BUT...

What if you could get the same gains as the $150.00 aftermarket CAI, for less than half the price?  Well, you can from a CAI made from simple parts that one would find at most hardware stores.  If you can change your own oil, and you own some basic hand tools, you can make a cheap, good looking CAI for your Mustang.  In the process, you'll save a little money for parts that you can't make, like a new camshaft. 
Shopping List
Pictured on the right is everything you will need to make a CAI.  Pictured from the top left, working clockwise:

-4 bolts with nuts
-small rubber PCV gromet for breather line
-4 hose clamps that close to at least 3-1/4", but open to at least 3-1/2"
-2 jointless rubber couplings
-K&N RU-3130 (7" conical filter)
-aluminium or plastic plate (aluminium needs to be 1/16", plastic 1/8")
-straight tubing to make spacers
-gasket material
-at least 10" of 3" inner diameter PVC or ABS plastic tubing
-45deg PVC or ABS plasitc elbow with one "street end" (no coupling) and the other with a coupling.
-Pro-M 75MM Bullet

not pictured: can of spray paint (I chose black, but this is up to you), and blue RTV.

Note: The stock MAF can be substituted for the Pro-M
The stock replacement K&N can be used with minor modifications to the following procedures.
Tools Needed:
-pipe cutter
-hack saw (or some other method of cutting the PVC pipe)
-wrenches or ratchets
-utility knife
-150 grit sand paper
-800 grit sand paper
-Dremel type tool with sandpaper rolls (opitional)
-Hand drill with bits
-3-1/2" circle cutter drill bit
-tin snips
On to: Constructing the CAI
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