Take the header off, then where the 2 pipes go into one, there is a seam. Take a screwdriver and measure the distance from the end of the header where it is now one and the cat. mark that measurement on the top then mark another point just past the seam toward the front of the header. I cut 3 side of the rectangle and folded the cut flap backwards exposing the cat. Secure the headers and start banging away with a hammer and chisel to remove the cat. The secret is to break it up in small pieces. When cat is all out and all is cleaned up, then fold the flap back down and weld shut. Just to make sure, I cut the top of the headers so that you cant see any welding marks from underneath and its all hidden under the bike.