Covered many many many many many many times.
Good for sound and show.
They DO NOT increase performance.
The zed has an intelligent ECU which dials back any gains to stock levels. So even if the heat soak didn't effect you, then you still wouldnt see a gain.
But they look good and sound great - if you like that kinda thing. And you won't notice any lost ponies from the heat soak in every day driving.