I’m not going to go into detail on the process taken to swap out the standard catalytic converter for a decat pipe as there is a very good write-up available on IMOC here.
I will mention however that you shouldn’t even attempt the job without a set of Irwin bolt grip extractors (there are cheaper places to get these, the link is just an example) and a lot of WD40 or PlusGas for lubricating the turbo-cat bolts. You will also need a breaker bar or long torque wrench for cracking the bolts off.
The job took me 6 hours on my own and I am now able to do it in 3 hours now that all the bits have been on and off. When refitting after the MOT I also fitted a support bracket from JSP to help prevent the decat cracking due to engine movement. The bracket holds the decat to the engine block (uses an existing bolt from the oil cooler – highlighted in picture below).
For reference, part numbers used were:
* cat retaining bolts – 90179-10094
* turbo to cat gasket – 17279-88381