When looking up to find out if I needed a cat or not found the following.
www.gtfours.co.uk/images/mot-cat.gif
And this image.
So basically as the gen 5 are gtr not gti and the gen 6 areareSSI SSII etc not GT ST SR, they technically can't be tested for having a cat. I'm also aware that if you get a letter from toyota stating the car was not made for UK market that they have to use a non cat test standard. I'm away to fleabay to order a nice stainless steel decay.