when i had my stocker on i removed the silence with a pair of Screw driver, vice grips and a hammer, you will not salvage the silencer this way.
I used the screw drive to tap between the silencer and the outer pipe, then i clamped the vise grips on it and tap it with the hammer until i started to break free.
One i was able to turn it a bit i was able to pull it out. It did take like 1/2hr to get it out, so be patient. i also bought a spark arrestor tip for the muffler to clean up the marks from taking the silencer out, and it gave me a spark arrestor again for legal trail riding
I took the little bolt out of the bottom of mine and grabbed it with a plyers and it pulled out, did it the same way on a friends YFZ. Take out the bolt and ride around for a while, it'll come out eventually. lol