I've had mine blow out twice now. I've cut the cover off and re-welded the bung and an extra washer over top and heat wrapped my pipe.
I beleive the heat sheild eventually gets sloppy from bouncing around on the pipe and hammer's out the insulation, then bounce's off the bung, eventually fatiging it enough it cracks and blows out. Stock pipe's are actually preferred for boost'd sleds as they are thicker then most aftermarket pipes.