My experience with the 2 new PFR pipes I have purchased and fitted over the last 2 years have been poles apart. Both have included the PFR alloy muffler as well.
On my YZ400D the pipe just fell on .. no modifications required at all, a perfect fit. Couldn't be happier.
But on my YZ250D I had to make/source different insulated pipe mounts but that was after I had to grind some of the cylinder head fins away by as much as 10mm at the rear of the head. It was such a bad fit I called the supplier to let them know they had sent the wrong pipe but alas it was the right one