If I change my OEM fitted exhaust manifold , to another one with improved air flow… As long as it has a cat is fitted is it still road legal? and could everyone recommend a suitable system, Im looking a BBR type.
Thanks
Another can of worms. There have been numerous posts on this.
I have a catless manifold fitted which should be a guaranteed fail yet it has passed two mot’s since 2018.
The letter of the law seems to state that no element of the car’s emission control system should be modified. I would argue that an aftermarket exhaust catted or not is a modification if it is not of the original design and spec. The issue is not the ability to pass emissions limits but rather the modification itself.
The bbr and other catted manifolds are plugging a gap in the market while having a foot in each camp.
I would say buy a 4-1 catless and keep the original you take off as insurance.
Thank you.
I agree entirely with mk375 except the part of a “guaranteed fail”. *
I also have a non catted manifold, which passes the MOT.
(BBR are certainly trying to have their cake and eat it. They are not transparent in the sales blog etc).
*If it was, then at least one of our modified cars would have been failed by now. I have researched and found NONE that have a catless manifold have been failed. Quite a few people state it should (I don’t) unless someone can prove to me with evidence that it should.
I will state again, are all the Testers turning a blind eye or incompetent? No of course not.
Likewise, it has been confirmed that a Tester is NOT allowed to use prior knowledge when testing a car.
You have to test it on what you can see and what the emissions results are.
I am still convinced if the car passes the emissions test then that’s what all the legislation was written for.
Likewise, when a central cat fails and is replaced with an aftermarket one, then are people saying that “Technically” that should also fail?
Quite a few people have replaced the central cat and not been failed because it is not the original Mazda one.
You could say the same about aftermarket suspension, brakes or whatever…
As stated above numerous threads on here and have a read of this one regarding the debate.
A can or worms indeed.
Good luck with your mod no matter which route you take. 
Thank you for a fast and detailed response. Could you help with one more point please? To get the best out of this mod, cat or no cat, is it best to get the car’s ECU re-chipped as well, or just enjoy the extra power from the new 4 into 1 on its own. Thanks again!
Hello Jim_G
Roddisons Motorsport Sheffield S9 1US 0114 244 5300 ask for Paul.
Roddisons did the following to my 2014 2 litre Sport Tech Recaro:-
Catless 4 into1 manifold, stainless centre section plus 200 cell cat, stainless back box
& ECU modifications in 2017 which is when I bought the car from Paul.
No problems with MOT’s, just make sure the engine is really hot for the emission test.
Yes, Colchester to Sheffield is a fair distance. If you do entrust your car to Paul then
get 4 wheel alignment & corner weighting done, maybe a service with gearbox & diff oils changed. The gearbox oil that Paul uses certainly made for a really smooth 1st to
2nd gear change even in cold weather.
Regards
Keith
Keith
Many thanks, I will look him up.
In my opinion yes. You will get the tuning mapping done for your car and not a generic one. You are a bit limited where you can go now. Mine was done at Skuzzle which is unfortunately shut now. 
. But I would have a weekend away in Sheffield and visit Rodders. 
Thanks… A weekend in Sheffield is needed. Do you rate BBR at all… A bit closer for me to travel.
I can’t comment on BBR. (Not used). So that would be unfair of me to do so. But many do rate them. Speak with them both and see which you feel comfortable with. There are other specialists out there too, so hopefully some one else will come along to give you some information.
Hero… thanks
Never been a hero😂 but thanks.
Just an opinion but research it to death before you commit too. Likewise, check with your insurer. I had to change mine. Funnily enough Admiral were happy and not that expensive. I informed them what package/had been done and they were fine. They stipulated that the additional modified parts would not be covered. Well if the manifold in these gets damaged then the whole car would be written off anyway!
Personally, I love it and as I have said before it make a great car greater! Enjoy and good luck with everything
Sanspeed at bexley heath may be more convenient for you.
Thanks. I will look them up, certainly a lot closer!