That's weird becuase i have those same headers (mine aren't coated) and they don't make that noise. It could be an internal engine noise (worst case scenario). Good luck
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'84 Mustang 5.0 T5, FMS aluminum radiator & 180* thermostat, 1 5/8 shortys/2.5" duals, '88 GT tail lights and wheels, Holley 4160 4 BBL, smog pump idler, now with hi-po collapsed lifters in #3 or #4
