existing stock i.c.? Thanks!!

Intercooler really isn't anything too high-tech :-) It really is just like your radiator and passes hot pressurized air in to several chambers that get air cooled from the outside air flow as you drive. As well as the surface area from the metal IC. A FMIC replaces the stock IC.

cp

When air is compressed air gets heated. Hot air makes the combustion more prone to pre-ignition (pinging) at boost. The intercooler (charge air cooler) removes most if not all (depends on type, i.e air to air, air to liquid, placement, and efficiency of the device) of the added heat. thereby letting more boost accepted before pre-igntion begins. An added benifit to an intercooler is that a cooler air charge is more dense than a heated one, there is more 02 to help the combustion.

So in a nutshell, cooler air = more allowable boost + denserair = more power.

...isn't a good idea. The OE unit is somewhat restrictive (above 5K rpm) and adds unnecessary volume (source of noticable turbo lag to some) to the intake tract.