I ran mine without a BOV with no problems IMO only really sounds decent when the filter is relocated to the front bumper. But what was even better was open turbo, no mesh or filter just open ;) I had to move my car and I had sold the filter relocation so had to drive it with nothing and my god it was so loud loved it if I could get away with running nothing I would But I have a Greddy Type S to go on once my build is ready Anyways good progress mate love the way this car is heading