I received mine last Tuesday, and to be perfectly honest, I wish I had just bought new mufflers. Nothing wrong with their products, but a real pia to install. My bike is only 10 months old with 4500 miles and I thought I would never get the old cores out. Grinding the welds was a small part, but driving the cores out took a 30" piece of 1 1/4" pipe and a 4lb hammer. Mine were only welded in two places each. I installed the new blankets and expanders and the bike sounds better and still not very loud. I also kept the original header pipe.

 

I've done them on my last two. Found the easiest way to get cores out after grinding is to stand up that 1.5" pipe and use the muffler like a slide hammer so your sliding the muffler down onto the pipe. Usually come out pretty quickly like that.