A cold air intake kit basically does what your stock intake does. It sucks air from your fender where it isn't heated up by the engine. It's cold relative to taking air from inside engine compartment which some of the conical filter setups do. If they produce more power, it is probably more likely because of the smooth tubes reducing turbulence in the intake.
Ram air is only really good at high speeds (above 100mph).
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351W 89 Mustang GT Convertible