mine does it some too..but not real bad.. usually a small air leak into the exhaust does it..is it just one loud one or kinda burble? run fine otherwise? if it runs fine, you might loosen the H-pipe from the headers and re-tighten it.. cant hurt to change the 02 sensors while your down there either ;-)
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84 convt,'95 302,AFR's, performer
3.55's, underdrives shorties
14.16@100.08
and a '68 stang that WAS nasty ;-)
MY ride