I believe my car has a pretty good manifold leak. They whole exahaust has been replaced except for the manifolds, and the sound still exists. I can hear it bouncing off the curb all the time and it gets on my nerves. How are the manifolds attached to the block. Obviously by bolts, but is there a gasket or anything in between the two? I suppose I can try tightening the bolts, but I doubt it will do any good. Any other suggestions?