Just because I own an NA doesn't mean I've never been in a tt z. I've been in a stock one, and I've been in a modified one with blow off valves. Bottom line is, there is no substantial proof that they are better than the stock recirculation valves. Which would also mean that there is no justification for wasting that much money on a product that goes pshh every time you let off the gas. Kinda annoying actually. I like listing to my stereo without having some random high pitch noises thrown in there.