1st ,take the system off. lay it on the ground the way it came out of the truck. Get out yer cut off wheel and cut the cat right above the seam, all the way around. Take the top off and pull out the insides. Weld back on. If you dont have the tools you could alwys go w/ the old hammer and punch method. I do not condone this, it is illegal. Just had to add that in. Big Brother is always watching!!