I though that my gaskets went bad in my older connections after I installed
the new CAT and muffler last week since I was getting the loud "broken pipe"
sounding exhaust. I put some silicone around where the gaskets connect to
check and let it dry. Today the silicon was still in place after driving
around. So I investigated farther and discovered the hole for the O2 sensor
in the CAT. I must not have been paying attention as this must have been
some plastic cap or something since now it's gone. This is apparently my
exhaust leak.  Does anyone know if there is a size bolt I can stick in there
or should I just plug an old 02 sensor in there to plug it up?

Thanks,
Bryan