Brake booster to MC, vacuum seal or dust boot?

[cst350]

Putting new calipers and rear cylinders on today. Got to the point of bleeding and realized the MC was dry in the back. Took it off to bench bleed and found a good tear in the rubber part between the Booster and MC. Researched as many threads here and elswhere as I could but there seems to be a variety of opinions as to weather this part is a vacuum seal or a dust shield. So... do I order a new one and wait til next weekend or do I put it back in and continue??? Apart from the tear the part looks pretty clean.