Yep, it's not a simple 90 degree silicone and the top section is oval. From memory I think an 81 or 82mm round pipe can be manipulated to fit on to the airbox, and the turbo end is about 60mm.
I made something similar a while ago when I used a factory MAF housing as part of my intake, made quite a difference, lot less restrictive than the standard silly plastic flexi pipe thing though