Never heard of reversing the DV not sure if its sate either
Think before you post.
Reversing the DV is 100% safe, and just changes the speed at which opens, and the boost pressure which it can withhold before being forced open.
All is it is a valve that opens to let air through.
in the 'standard' orientation charge pressure pushes onto the side of the valve, and the valve is pulled open by the vacuum force on gear changes.
when reversed, charge pressure goes into the 'bottom' of the valve, pushing directly against the piston. This is where the spring tension is more important, as the piston is held shut against boost by the spring tension, and the small positive pressure from the vacuum line in the top of the DV. in this case, when you back off, the vacuum line goes to negative pressure, and the boost on the bottom of the piston instantly forces it open.
Running the DV backwards gives a quicker response, and you'll find it's 'dumping' much more often, and it's a different sound, as it's more short and sharp. Running it backwards tends to be fine on standard cars, although when running high boost, even with a yellow spring it'll still leak over about 18psi.