I cleaned up a pair of y-pipes on a Lusso exhaust I was working on. They were in good shape, but had some surface rust that I wanted to remove and paint with some high temp exhaust paint.
Looking down the flanges, I found a pretty heavy weld securing the flange to the pipes. I don’t believe this was how Ferrari would have done this.
I got out my die grinder and smoothed out the transition and made the exit diameter between the connection the same. I don’t know when a restriction like this will make the biggest change, but removing it has got to help!