The honeycomb inside the catalytic converter might be broken. The best thing to do is start the car & look underneath to see where the sound is coming from. If it is the honeycomb, then you can get it taken off & flushed which means opened & emptied. Hope that helps a bit.
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89 coupe, 351W, 351W heads, 30lb injectors, 190lph pump, 80 maf, 70 tb, ? cam, cobra upper, gt 40 lower, 4.10s, (14.1@98)
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