An engine is a system. All the parts need to fit together with a particular performance goal in mind. If the cam doesn't match the heads, the carb, the intake manifold, the displacement, the compression ratio, the rear axle ratio, the ignition curve, performance would go down, not up.

Your post reads like you want a cheap cam with a rough idle. That's not much of a performance goal, and there's not enough info in your question to provide a meaningful answer.

By the way, you can get a rough idle by messing with the fuel mixture. No need for a cam. Besides, you just slammed the guy who is the most able to provide you info.