The pipe was probably tack welded inside the outer shell, to the rear plate and to some baffles. It is possible/probable that the installer clamped the pipes into place before hanging everything and letting all joints find their own 'home'. This causes all the parts to fight each other. See if you can find a cooperative Walker dealer for warranty replacement or try to locate their customer service 800 number. The front is really just a resonator and can be replaced by a straight pipe.