Has anybody ever had an exhaust leak emanate from the beveled flange joint where the end of the header pipe pictured below, mates to the front part of the cat converter pipe? I started hearing the exhaust leaking under acceleration yesterday on the way home, and the fumes were coming inside the car. I'm told there is not a flange gasket on these, only the beveled fit to prevent leaking. See attached. I just tried to snug these flange bolts up, but they didn't seem loose, and it made no difference. Can still hear and smell the leak. Is it even possible for these to come loose and leak, and has anyone here ever experienced this problem? Another thing I noticed is that it almost seems that the leak is originating from the BACK of the engine block, not below it. Does anyone know if there is some kind of an exhaust inlet to the rear of the block that might leak? Been trying to find an aft side pic of my 3.9L V6 on the web, but no luck so far. 2004 3.9 V-6 @ 160,000 miles. Thanks!