a mate of mine had a stage 3 car t34, no dv. turbo stalled and the turbine shattered, sending all the pieces into the intercooler and a few found there way into the engine and killed it dead!
Air going the wrong way through a turbine can only be bad and cause damage,
they just are not designed for that sort of abuse, if you run no dv the risk s all yours cos i dont want it!!! it may sound nice but so does running no air filter but it obviously isnt good for the turbo or engine.
I always run a dv!!