Your stock set up already has a BOV that vents back into the intake tract so the sound is muffled. The Morpar BOV plate is added on to the stock one and vents to the outside and the noise is more noticeable.
The stock BOV is a bit restricted by the small size of the plumbing so the Mopar BOV plate will allow more efficent venting. The Stage 1 upgrade is supposed to be designed to be used with the BOV plate (but not absolutly necessary). There are some other, more expensive aftermarket BOVs that are adjustable. These may be a little over the top for a street driven car.
I could go on about why turbos need a BOV vent at all, but that's another story.
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