Sounds like the noise is coming from y pipe/manifold area. I took both y pipe apart to be able to move exhaust and still could not get at the donut gasket to replace it. I could inspect it and it looks worn but not bad. Am I missing something here to make this easier to remove? I just couldn't get enough clearance to remove it. I hope I dont need to remove the manifold to do this seamingly easy repair. All manifold bolts were tight and gaskets looked ok from what I could see. Thanks for your help.