Clogged CAT

Either I have a restricted exhaust or my CAT is clogged. I mostly beleive my CAT is clogged because I'm hearing the same rattle sound I heard from the old one before the catalyst broke into pieces. I have bad MPG and slow performance as the car is hot. When I put the new CAT on I changed the wires, plugs, o2 sensor, and muffler. So what else is causing my CAT to go bad, could it be my CAI? I checked my coil packs they're good I don't think I'm leaking coolant in my gaskets. What else could it be?

What yr and when did you change it.Your CAI shouldnt have nothing to do with it .Do you have any codes.

its a 92 sse. I ran the actron scan tool and have no codes. I did all this about a month ago now. I noticed a small tiny leak from my water pump, but it isn't a lot, looks like its leaking out real slow because its the drip been in that position. I do have a lifter problem because I hear ticking everytime I start my car, but I wouldn't think that has anything to do with clogging my CAT. The CAT looks over heated too because the bottom of it is a brown burned color.