a DV doesn't put air back into the turbo on intake side to keep it spinning; a DV relieves the pressure between the turbo and intake manifold when the throttle.
without a DV, the compressed air will go back towards the turbo putting huge strain against the compressor fins and the turbine shaft aswell, as the air is going AGAINST the direction of rotation/air flow in the turbo. This will ultimately kill a turbo, or reduce its life severely.
a Vent to Atmosphere DV may not necessarily throw up any codes, but i would pretty much guarantee a worse MPG than with a recirc DV. This is because the ECU will expect the released air to still be "in the system" post MAF, but with VTA DV this is removed from the system. So the Air/Fuel mix will be slightly differently (more fuel, less air) = richer running, and potentially less MPG / Fuel efficient.
that's my view anyway...I'll let TT correct any errors!