I had an issue with my cat, I divorced her. All kidding aside, on my old trusty 90 teg my cat was melted inside, I felt a power loss and it made funny noises. When I took it off the inside of the cat honeycombs were melted away on the side that the downpipe connected to it. Really bad. Parts of the honeycomb were breaking off and sticking in the cat and then getting shot out the exhaust, hence the funny noises. I had wrapped pacesetter headers at the time. I replaced the cat with a random technologies freeflow cat and put on some Neuspeed N2 headers and finished it off with a Greddy SS catback exhaust. Problem solved!