30-09-2014, 03:52 PM
Personally, I would just do as Rob says above and have the CAT "shell" in place but gutted or with a pipe welded inside. That way, it will pass an MOT or VOSA check just fine as they're not going to remove it from the car to check whether there's anything inside it, merely just a visual check that there is something that looks like a CAT (and/or a DPF) present in the exhaust.
1990 Peugeot 205 GTi 1.9 // 1991 Peugeot 205 GTi 1.9 16v // 1992 Peugeot 205 GTi 1.9 // 1999 Peugeot 306 HDi Estate