While replacing the rear motor mount, I noticed that exhaust gases would be seeping out of the gasket between the j-pipe and the second catalytic converter. It was also noisy. I finally got around to replacing the donut gasket, but it is still loud. I re-used the existing springs that go on the bolts (connecting the j-pipe and catalytic converter flange) with new bolts and nuts. Maybe that's the issue. A couple of seconds after I start up the car, I see water dripping out of the gap where the donut gasket is. So, if it isn't water-tight, it isn't air-tight. The next step I am going to do is is get new springs and use exhaust gasket sealant too.