I agree with Randy. Our muffler systems may have minor leaks due to fitment issues at the pipe connectors, but at the header and downpipe it's more likely the installer doing something excessive, like wrestling the system around too much with the front muffler bracket unhooked and maybe also a broken bracket at the downpipe heat shield, such as when trying to disconnect or fully the pipe joints. There's also the possibility of the whole muffler system being hit from the rear, like backing into a low wall or high curb.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now