In my 1990 e34 I had to go thorugh replacing the entire exhaust system including the cat. When I removed it I found a large gash and lots of leaks. I thought about a factory type replacement but the price was way too steep. I went with a DEC cat from the ultimate garage. Fit perfectly came with all required hardware. Happy so far. There will be a lot of white smoke when you first run the new cat (panic attack), but it will clear up after a couple hours.