Maxwell,

The "square thing" is just the top pf the "y" pipe assembly.

There's a sort of dished "lid" attached by a set of torx screws.

No mods were needed except I had to remove the rubber seal inside the "y" pipe where it attached to the MAF. The Crossfire MAF is about 1/8" too big for the Benz "y" pipe. I'm using a fat elastic band a a seal now. It is actually a drive belt for a sweeper; origin unknown. Just a big tough rubber band really. Nice snug and no leaks. I'll replace the industrial strength zip-ties with stainless band clamps in the next few weeks for a more "factory" look.