Hi Sammo,
your signature line sez "open pipes"
If you opened them like I opened mine by driving a pointed steel bar into the stock mufflers to puncture the baffles, the stock muffler crosspipe is still there.
It's joined in the middle with a clamp and a crush sleeve and that joint can be a right swine to undo.
You can make a little threaded rod, nut and tube jack to force the joint apart after you have removed every last fastener holding the exhaust in place and slathered the joints in penetrating oil.