Exhaust Help

95 Tacoma 2.7 had the check engine light on and came up with catalyst efficiency low bank 1. The o2 sensors were reading the same. I found that the gasket before the Cat was leaking. I replaced the gasket and cleared the code. It was fine for about 50 miles and then the light came on again. I can hear the gasket leaking again. First thought was the cat was pluged but it was replaced before i bought it a few months ago. If the muffler was pluged from pieces of the old cat i figured the gasket aftrer the cat would blow. Any ideas of what would cause it? I might take the cat off this week to see if it may be pluged for some reason.

i just took the cat off and its rattling alittle bit. I can still see through it but what would cause a new cat to rattle when its only a few months old

sounds like the cat is defective, is the engine running fine? sometimes if you overheat a cat, they will do that