Getting ready to install headers this morning (til the rain rudely interupted) When we were looking at the y-pipe & can't figure out how it attaches to the cat. Theres no clamp. Seem to be 1 piece. The new y-pipe has a flange on it. The cat doesn't. Help please!

 

The stock Y-pipe and catalytic converter are welded together. For an aftermarket cat/y-pipe you can either have a flange installed to bolt them together or weld them.

Aftermarket exhaust parts never seem to be friendly to the home installer who can't weld and/or modify