I have now tried about everything in the book to try to get rid of this sound that sounds like an exaust leak, but now I am not to sure. I cut the header flanges, so they are not warped, new ultra seal header gaskets with MEGA COPPER high temp sealer on them. As for the collecters, dead soft copper gaskets with high temp seal, and still this noise persists. It makes my truck sound like apiece-O-[darn]. could it be anything else?