mine is bolted with a home made bracket to the metal bracket which holds the dipstick and n249 valves on later 1.8t`s. I have ordered a bung for the TIP connection and a breather filter for the outlet of the can so nothing goes back through the inlet.perhaps that will help.
No reducer just adapters, I can't remember what thread the catch can has off the top of my head but I think it was 3/8