It's been talked about loads of times tbh, there aren't many available, Mugen which is big bucks, some go for the Spoon 4-2 then swap the decat section for the OEM cat come MOT time again expensive, Piper do one and so does Japspeed.
They tend not to make as much power as the 4-2-1's so is it worth it over cost. Some have been happy with the Piper but again it's cost and performance is it worth it scenario.
I've heard from a good source that the Japspeed 4-1 and 4-2 can make less power than OEM and it's better to stick with OEM than go for the Japspeed. (The Japspeed 4-2-1 has good ratings though but as most 4-2-1's they remove your cat).
Some have used the DC5 manifold and cat, that's the route I'm going with, got one off a pal cheap haven't fitted it yet though.
Some of our neighbours abroad have welded a sports cat to the Tegiwa manifold but that will void any warranty and if you mess up you've wasted your money.
It's a difficult one that's had many scratching their heads, most just go for the 4-2-1's and have a friendly MOT tester or swap back come MOT time but the friendly MOT testers are getting difficult to come by plus the law are clamping down so wouldn't want to take the risk of having my car crushed. Swapping out can be a pita unless you know what your doing and can do it yourself etc.
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