i just installed the seibon DV hood on my car and I'm pleased with how much heat it's letting out. You can literally see the heat radiating out now, and thats barely even pushing the car very hard.
For anyone that doesn't run a vented hood, I would highly recommend it.
I was always against vented hoods for cosmetic reasons, but the DV from seibon keeps the factory lines and the two large horizontal slits are large enough to act like a chimney.