You could build your own cold-air intake setup for about $50, but you can also buy one for about $100. You'll gain like 1-2hp at the most. A better recommendation for making some power naturally aspirated would be to find a ranger exhaust manifold, A237 cam, free-flowing exhaust, port/polish heads, and maybe higher compression. You could make ~140hp with these mods.
For a turbo swap, you'll need to find a donor car. The most popular is a Thunderbird Turbo Coupe (TC for short). You can pull out the motor, and drop it into your current Mustang with minimal modifications (exhaust, splice a couple wires, and a new ECU), for anywhere between $500-$2000, depending on what kind of/how many parts you buy for it, and how much overhauling you do. With ~15lbs boost, volvo front-mount intercooler, a full 3" exhaust, and a big Vane Air Meter, you can expect to make about 230hp or so.
Bolting up just a turbocharger to your current 2.3 isn't a good idea, since the cast pistons will probably blow up once the engine detonates once.
Pro-Hawk, the correct link for Mike SVOR is:
http://msvorinich.itgo.com/