best way i have found is to grab an old masonry chisel that has copped a beating so the end is flattened a bit like this


then grab some vise grips and clamp onto the sharp end

shove it into the exhaust so the lip on the end of the chisel 'grabs' the inside of pipe & then pull it out like a hammer motion, keep doing it & it will eventually come out, best part is this doesn't physically ruin the appearance of your silencer from the outside