Replacing the flywheel does generally give you benefits depending on the car. Some cars have a flywheel in the 30 to 40 pound range. So changing it to a 15 pounder will definitely help rev the engine faster, and has given instant noticable difference.On the other hand, going too light on a flywheel, such as a 8 pounder, may make your idle a bit rough or stall a car, since it does not have the mass to keep it rotating. More likely a problem on a large displacement engine.Your civic most likely has a pretty decent weight to it, and is a small displacement engine. What you can do is change the clutch, and when the flywheel is out, have it shaved down a bit and balanced. Not sure the price but could be $75. Or maybe you get lucky and find a clutch and flywheel together on ebay or craigs list.