The airbox has two pipes because the S/RS cars have twin turbos. (Btw, that box looks like it’s from an S car, not an RS - The RS has a “grill“ on the top right corner of the airbox)
You should be able to use the single pipe connection from your TDI as I believe the actual box part is common across a number of models.
Not sure your going to get any gains from fitting the S box, as it’s identical to the standard box internally