This question may not be as cut-and-dry as mentionned earlier.
While I clearly agree that too big a carb is bad, simply improving on the airflow in and out of the engine will gain some noticeable power. A better intake manifold and better flowing exhaust, even with original carb (in condition and tune) and exhaust manifold will make a difference. Indeed, headers are not good for the street, but freer flowing after the manifold is good.
All this to say that we can (fairly easily) improve on the OEM "air pump" without big mods on the engine inside. Just not with a bigger carb!
