Okay this is what I would do, if the current gasket is still in one piece I would go buy some RTV gasket maker and put it on both side of the gasket then while your TB is off clean the ports a bit more and tighten those four bolts nice and tight. This would really seal it up you only need a very little bit so just smear it evenly in a very thin layer. If the noise it still there then it has to be something else.