A stage 3 flywheel!
It all depends on how and where you will drive your car.
A lighter flywheel will take less hp to spin, so you`ll be having more of your hp to the wheels. But at the same time, when you get off the gas, the revs o your engine will fall faster.
So if you go extra light, and if you get off the gas quick and not hold it, it can shut off your engine.
It will not give extra HP to the engine, but will free some of the engine`s HP and allow them to spin your wheels instead of the flywheel.
In everyday trafic will be hard to dive the car with an extra light flywheel, but if you only use it for racing, yo can go as light as you can.